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Comparing jsr166/src/jsr166y/ForkJoinWorkerThread.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.35 by dl, Wed Jul 7 19:52:32 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import java.util.concurrent.locks.*;
12	<	import sun.misc.Unsafe;
13	<	import java.lang.reflect.*;
10	>
11	>	import java.util.Random;
12	>	import java.util.Collection;
13	>	import java.util.concurrent.locks.LockSupport;
14
15		/**
16	<	* A thread that is internally managed by a ForkJoinPool to execute
17	<	* ForkJoinTasks. This class additionally provides public
18	<	* <tt>static</tt> methods accessing some basic scheduling and
19	<	* execution mechanics for the <em>current</em>
20	<	* ForkJoinWorkerThread. These methods may be invoked only from within
21	<	* other ForkJoinTask computations. Attempts to invoke in other
22	<	* contexts result in exceptions or errors including
23	<	* ClassCastException.  These methods enable construction of
24	<	* special-purpose task classes, as well as specialized idioms
25	<	* occasionally useful in ForkJoinTask processing.
26	<	*
27	<	* <p>The form of supported static methods reflects the fact that
28	<	* worker threads may access and process tasks obtained in any of
29	<	* three ways. In preference order: <em>Local</em> tasks are processed
30	<	* in LIFO (newest first) order. <em>Stolen</em> tasks are obtained
31	<	* from other threads in FIFO (oldest first) order, only if there are
32	<	* no local tasks to run.  <em>Submissions</em> form a FIFO queue
33	<	* common to the entire pool, and are started only if no other
34	<	* work is available.
16	>	* A thread managed by a {@link ForkJoinPool}.  This class is
17	>	* subclassable solely for the sake of adding functionality -- there
18	>	* are no overridable methods dealing with scheduling or execution.
19	>	* However, you can override initialization and termination methods
20	>	* surrounding the main task processing loop.  If you do create such a
21	>	* subclass, you will also need to supply a custom {@link
22	>	* ForkJoinPool.ForkJoinWorkerThreadFactory} to use it in a {@code
23	>	* ForkJoinPool}.
24		*
25	<	* <p> This class is subclassable solely for the sake of adding
26	<	* functionality -- there are no overridable methods dealing with
38	<	* scheduling or execution. However, you can override initialization
39	<	* and termination cleanup methods surrounding the main task
40	<	* processing loop.  If you do create such a subclass, you will also
41	<	* need to supply a custom ForkJoinWorkerThreadFactory to use it in a
42	<	* ForkJoinPool.
25	>	* @since 1.7
26	>	* @author Doug Lea
27		*/
28		public class ForkJoinWorkerThread extends Thread {
29		/*
30	<	* Algorithm overview:
30	>	* Overview:
31		*
32	<	* 1. Work-Stealing: Work-stealing queues are special forms of
33	<	* Deques that support only three of the four possible
34	<	* end-operations -- push, pop, and deq (aka steal), and only do
35	<	* so under the constraints that push and pop are called only from
36	<	* the owning thread, while deq may be called from other threads.
37	<	* (If you are unfamiliar with them, you probably want to read
38	<	* Herlihy and Shavit's book "The Art of Multiprocessor
39	<	* programming", chapter 16 describing these in more detail before
40	<	* proceeding.)  The main work-stealing queue design is roughly
41	<	* similar to "Dynamic Circular Work-Stealing Deque" by David
42	<	* Chase and Yossi Lev, SPAA 2005
43	<	* (http://research.sun.com/scalable/pubs/index.html).  The main
44	<	* difference ultimately stems from gc requirements that we null
45	<	* out taken slots as soon as we can, to maintain as small a
46	<	* footprint as possible even in programs generating huge numbers
47	<	* of tasks. To accomplish this, we shift the CAS arbitrating pop
48	<	* vs deq (steal) from being on the indices ("base" and "sp") to
49	<	* the slots themselves (mainly via method "casSlotNull()"). So,
50	<	* both a successful pop and deq mainly entail CAS'ing a nonnull
51	<	* slot to null.  Because we rely on CASes of references, we do
52	<	* not need tag bits on base or sp.  They are simple ints as used
53	<	* in any circular array-based queue (see for example ArrayDeque).
54	<	* Updates to the indices must still be ordered in a way that
55	<	* guarantees that (sp - base) > 0 means the queue is empty, but
56	<	* otherwise may err on the side of possibly making the queue
57	<	* appear nonempty when a push, pop, or deq have not fully
58	<	* committed. Note that this means that the deq operation,
59	<	* considered individually, is not wait-free. One thief cannot
60	<	* successfully continue until another in-progress one (or, if
61	<	* previously empty, a push) completes.  However, in the
62	<	* aggregate, we ensure at least probablistic non-blockingness. If
63	<	* an attempted steal fails, a thief always chooses a different
32	>	* ForkJoinWorkerThreads are managed by ForkJoinPools and perform
33	>	* ForkJoinTasks. This class includes bookkeeping in support of
34	>	* 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 activate if necessary before
78	<	* stealing (see below).
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 stolen) the most recent task it stole
89	>	* from some other worker. Plus, it records (in field joining) the
90	>	* 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 maintain per-task bookkeeping.  This
101	>	* requires a linear scan of workers array to locate stealers,
102	>	* which isolates cost to when it is needed, rather than adding to
103	>	* per-task overhead.  (2) It is "shallow", ignoring nesting and
104	>	* potentially cyclic mutual steals.  (3) It is intentionally
105	>	* racy: field joining is updated only while actively joining,
106	>	* which means that we could miss links in the chain during
107	>	* long-lived tasks, GC stalls etc.  (4) We fall back to
108	>	* suspending the worker and if necessary replacing it with a
109	>	* spare (see ForkJoinPool.tryAwaitJoin).
110		*
111	<	* Efficient implementation of this approach currently relies on
111	>	* Efficient implementation of these algorithms currently relies on
112		* an uncomfortable amount of "Unsafe" mechanics. To maintain
113		* correct orderings, reads and writes of variable base require
114	<	* volatile ordering.  Variable sp does not require volatile write
115	<	* but needs cheaper store-ordering on writes.  Because they are
116	<	* protected by volatile base reads, reads of the queue array and
117	<	* its slots do not need volatile load semantics, but writes (in
118	<	* push) require store order and CASes (in pop and deq) require
119	<	* (volatile) CAS semantics. Since these combinations aren't
120	<	* supported using ordinary volatiles, the only way to accomplish
121	<	* these effciently is to use direct Unsafe calls. (Using external
114	>	* volatile ordering.  Variable sp does not require volatile
115	>	* writes but still needs store-ordering, which we accomplish by
116	>	* pre-incrementing sp before filling the slot with an ordered
117	>	* store.  (Pre-incrementing also enables backouts used in
118	>	* scanWhileJoining.)  Because they are protected by volatile base
119	>	* reads, reads of the queue array and its slots by other threads
120	>	* do not need volatile load semantics, but writes (in push)
121	>	* require store order and CASes (in pop and deq) require
122	>	* (volatile) CAS semantics.  (Michael, Saraswat, and Vechev's
123	>	* algorithm has similar properties, but without support for
124	>	* nulling slots.)  Since these combinations aren't supported
125	>	* using ordinary volatiles, the only way to accomplish these
126	>	* efficiently is to use direct Unsafe calls. (Using external
127		* AtomicIntegers and AtomicReferenceArrays for the indices and
128		* array is significantly slower because of memory locality and
129	<	* indirection effects.) Further, performance on most platforms is
130	<	* very sensitive to placement and sizing of the (resizable) queue
131	<	* array.  Even though these queues don't usually become all that
132	<	* big, the initial size must be large enough to counteract cache
129	>	* indirection effects.)
130	>	*
131	>	* Further, performance on most platforms is very sensitive to
132	>	* placement and sizing of the (resizable) queue array.  Even
133	>	* though these queues don't usually become all that big, the
134	>	* initial size must be large enough to counteract cache
135		* contention effects across multiple queues (especially in the
136		* presence of GC cardmarking). Also, to improve thread-locality,
137	<	* queues are currently initialized immediately after the thread
138	<	* gets the initial signal to start processing tasks.  However,
139	<	* all queue-related methods except pushTask are written in a way
140	<	* that allows them to instead be lazily allocated and/or disposed
141	<	* of when empty. All together, these low-level implementation
142	<	* choices produce as much as a factor of 4 performance
143	<	* improvement compared to naive implementations, and enable the
144	<	* processing of billions of tasks per second, sometimes at the
145	<	* expense of ugliness.
146	<	*
147	<	* 2. Run control: The primary run control is based on a global
148	<	* counter (activeCount) held by the pool. It uses an algorithm
149	<	* similar to that in Herlihy and Shavit section 17.6 to cause
119	<	* threads to eventually block when all threads declare they are
120	<	* inactive. (See variable "scans".)  For this to work, threads
121	<	* must be declared active when executing tasks, and before
122	<	* stealing a task. They must be inactive before blocking on the
123	<	* Pool Barrier (awaiting a new submission or other Pool
124	<	* event). In between, there is some free play which we take
125	<	* advantage of to avoid contention and rapid flickering of the
126	<	* global activeCount: If inactive, we activate only if a victim
127	<	* queue appears to be nonempty (see above).  Similarly, a thread
128	<	* tries to inactivate only after a full scan of other threads.
129	<	* The net effect is that contention on activeCount is rarely a
130	<	* measurable performance issue. (There are also a few other cases
131	<	* where we scan for work rather than retry/block upon
132	<	* contention.)
133	<	*
134	<	* 3. Selection control. We maintain policy of always choosing to
135	<	* run local tasks rather than stealing, and always trying to
136	<	* steal tasks before trying to run a new submission. All steals
137	<	* are currently performed in randomly-chosen deq-order. It may be
138	<	* worthwhile to bias these with locality / anti-locality
139	<	* information, but doing this well probably requires more
140	<	* lower-level information from JVMs than currently provided.
137	>	* queues are initialized after starting.  All together, these
138	>	* low-level implementation choices produce as much as a factor of
139	>	* 4 performance improvement compared to naive implementations,
140	>	* and enable the processing of billions of tasks per second,
141	>	* sometimes at the expense of ugliness.
142	>	*/
143	>
144	>	/**
145	>	* Generator for initial random seeds for random victim
146	>	* selection. This is used only to create initial seeds. Random
147	>	* steals use a cheaper xorshift generator per steal attempt. We
148	>	* expect only rare contention on seedGenerator, so just use a
149	>	* plain Random.
150		*/
151	+	private static final Random seedGenerator = new Random();
152	+
153	+	/**
154	+	* The timeout value for suspending spares. Spare workers that
155	+	* remain unsignalled for more than this time may be trimmed
156	+	* (killed and removed from pool).  Since our goal is to avoid
157	+	* long-term thread buildup, the exact value of timeout does not
158	+	* matter too much so long as it avoids most false-alarm timeouts
159	+	* under GC stalls or momentarily high system load.
160	+	*/
161	+	private static final long SPARE_KEEPALIVE_NANOS =
162	+	5L * 1000L * 1000L * 1000L; // 5 secs
163
164		/**
165		* Capacity of work-stealing queue array upon initialization.
166	<	* Must be a power of two. Initial size must be at least 2, but is
166	>	* Must be a power of two. Initial size must be at least 4, but is
167		* padded to minimize cache effects.
168		*/
169		private static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
170
171		/**
172		* Maximum work-stealing queue array size.  Must be less than or
173	<	* equal to 1 << 30 to ensure lack of index wraparound.
173	>	* equal to 1 << 28 to ensure lack of index wraparound. (This
174	>	* is less than usual bounds, because we need leftshift by 3
175	>	* to be in int range).
176		*/
177	<	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 30;
177	>	private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28;
178
179		/**
180	<	* Generator of seeds for per-thread random numbers.
180	>	* The pool this thread works in. Accessed directly by ForkJoinTask.
181		*/
182	<	private static final Random randomSeedGenerator = new Random();
182	>	final ForkJoinPool pool;
183
184		/**
185	<	* The work-stealing queue array. Size must be a power of two.
185	>	* The task most recently stolen from another worker
186		*/
187	<	private ForkJoinTask<?>[] queue;
187	>	private volatile ForkJoinTask<?> stolen;
188
189		/**
190	<	* Index (mod queue.length) of next queue slot to push to or pop
191	<	* from. It is written only by owner thread, via ordered store.
169	<	* Both sp and base are allowed to wrap around on overflow, but
170	<	* (sp - base) still estimates size.
190	>	* The task currently being joined, set only when actively
191	>	* trying to helpStealer.
192		*/
193	<	private volatile int sp;
193	>	private volatile ForkJoinTask<?> joining;
194	>
195	>	/**
196	>	* The work-stealing queue array. Size must be a power of two.
197	>	* Initialized in onStart, to improve memory locality.
198	>	*/
199	>	private ForkJoinTask<?>[] queue;
200
201		/**
202		* Index (mod queue.length) of least valid queue slot, which is
#	Line 178 | Line 205 | public class ForkJoinWorkerThread extend
205		private volatile int base;
206
207		/**
208	<	* The pool this thread works in.
208	>	* Index (mod queue.length) of next queue slot to push to or pop
209	>	* from. It is written only by owner thread, and accessed by other
210	>	* threads only after reading (volatile) base.  Both sp and base
211	>	* are allowed to wrap around on overflow, but (sp - base) still
212	>	* estimates size.
213	>	*/
214	>	private int sp;
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.
221		*/
222	<	final ForkJoinPool pool;
222	>	private volatile int runState;
223	>
224	>	private static final int TERMINATING = 0x01;
225	>	private static final int TERMINATED  = 0x02;
226	>	private static final int SUSPENDED   = 0x04; // inactive spare
227	>	private static final int TRIMMED     = 0x08; // killed while suspended
228
229		/**
230	<	* Index of this worker in pool array. Set once by pool before
231	<	* running, and accessed directly by pool during cleanup etc
230	>	* Number of LockSupport.park calls to block this thread for
231	>	* suspension or event waits. Used for internal instrumention;
232	>	* currently not exported but included because volatile write upon
233	>	* park also provides a workaround for a JVM bug.
234		*/
235	<	int poolIndex;
235	>	volatile int parkCount;
236
237		/**
238	<	* Run state of this worker. Supports simple versions of the usual
239	<	* shutdown/shutdownNow control.
238	>	* Number of steals, transferred and reset in pool callbacks pool
239	>	* when idle Accessed directly by pool.
240		*/
241	<	private volatile int runState;
241	>	int stealCount;
242
243	<	// Runstate values. Order matters
244	<	private static final int RUNNING     = 0;
245	<	private static final int SHUTDOWN    = 1;
246	<	private static final int TERMINATING = 2;
247	<	private static final int TERMINATED  = 3;
243	>	/**
244	>	* Seed for random number generator for choosing steal victims.
245	>	* Uses Marsaglia xorshift. Must be initialized as nonzero.
246	>	*/
247	>	private int seed;
248
249		/**
250		* Activity status. When true, this worker is considered active.
251	<	* Must be false upon construction. It must be true when executing
206	<	* tasks, and BEFORE stealing a task. It must be false before
207	<	* blocking on the Pool Barrier.
251	>	* Accessed directly by pool.  Must be false upon construction.
252		*/
253	<	private boolean active;
253	>	boolean active;
254
255		/**
256	<	* Number of steals, transferred to pool when idle
256	>	* True if use local fifo, not default lifo, for local polling.
257	>	* Shadows value from ForkJoinPool, which resets it if changed
258	>	* pool-wide.
259		*/
260	<	private int stealCount;
261	<
260	>	private final boolean locallyFifo;
261	>
262		/**
263	<	* Seed for random number generator for choosing steal victims
263	>	* Index of this worker in pool array. Set once by pool before
264	>	* running, and accessed directly by pool to locate this worker in
265	>	* its workers array.
266		*/
267	<	private int randomVictimSeed;
267	>	int poolIndex;
268
269		/**
270	<	* Seed for embedded Jurandom
270	>	* The last pool event waited for. Accessed only by pool in
271	>	* callback methods invoked within this thread.
272		*/
273	<	private long juRandomSeed;
273	>	int lastEventCount;
274
275		/**
276	<	* The last barrier event waited for
276	>	* Encoded index and event count of next event waiter. Used only
277	>	* by ForkJoinPool for managing event waiters.
278		*/
279	<	private long eventCount;
279	>	volatile long nextWaiter;
280
281		/**
282		* Creates a ForkJoinWorkerThread operating in the given pool.
283	+	*
284		* @param pool the pool this thread works in
285		* @throws NullPointerException if pool is null
286		*/
287		protected ForkJoinWorkerThread(ForkJoinPool pool) {
237	–	if (pool == null) throw new NullPointerException();
288		this.pool = pool;
289	<	// remaining initialization deferred to onStart
289	>	this.locallyFifo = pool.locallyFifo;
290	>	// To avoid exposing construction details to subclasses,
291	>	// remaining initialization is in start() and onStart()
292	>	}
293	>
294	>	/**
295	>	* Performs additional initialization and starts this thread
296	>	*/
297	>	final void start(int poolIndex, UncaughtExceptionHandler ueh) {
298	>	this.poolIndex = poolIndex;
299	>	if (ueh != null)
300	>	setUncaughtExceptionHandler(ueh);
301	>	setDaemon(true);
302	>	start();
303		}
304
305	<	//  Access methods used by Pool
305	>	// Public/protected methods
306
307		/**
308	<	* Get and clear steal count for accumulation by pool.  Called
309	<	* only when known to be idle (in pool.sync and termination).
308	>	* Returns the pool hosting this thread.
309	>	*
310	>	* @return the pool
311		*/
312	<	final int getAndClearStealCount() {
313	<	int sc = stealCount;
250	<	stealCount = 0;
251	<	return sc;
312	>	public ForkJoinPool getPool() {
313	>	return pool;
314		}
315
316		/**
317	<	* Returns estimate of the number of tasks in the queue, without
318	<	* correcting for transient negative values
317	>	* Returns the index number of this thread in its pool.  The
318	>	* returned value ranges from zero to the maximum number of
319	>	* threads (minus one) that have ever been created in the pool.
320	>	* This method may be useful for applications that track status or
321	>	* collect results per-worker rather than per-task.
322	>	*
323	>	* @return the index number
324		*/
325	<	final int getRawQueueSize() {
326	<	return sp - base;
325	>	public int getPoolIndex() {
326	>	return poolIndex;
327		}
328
329	<	// Intrinsics-based support for queue operations.
330	<	// Currently these three (setSp, setSlot, casSlotNull) are
331	<	// usually manually inlined to improve performance
329	>	/**
330	>	* Initializes internal state after construction but before
331	>	* processing any tasks. If you override this method, you must
332	>	* invoke super.onStart() at the beginning of the method.
333	>	* Initialization requires care: Most fields must have legal
334	>	* default values, to ensure that attempted accesses from other
335	>	* threads work correctly even before this thread starts
336	>	* processing tasks.
337	>	*/
338	>	protected void onStart() {
339	>	int rs = seedGenerator.nextInt();
340	>	seed = rs == 0? 1 : rs; // seed must be nonzero
341	>
342	>	// Allocate name string and arrays in this thread
343	>	String pid = Integer.toString(pool.getPoolNumber());
344	>	String wid = Integer.toString(poolIndex);
345	>	setName("ForkJoinPool-" + pid + "-worker-" + wid);
346	>
347	>	queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
348	>	}
349
350		/**
351	<	* Sets sp in store-order.
351	>	* Performs cleanup associated with termination of this worker
352	>	* thread.  If you override this method, you must invoke
353	>	* {@code super.onTermination} at the end of the overridden method.
354	>	*
355	>	* @param exception the exception causing this thread to abort due
356	>	* to an unrecoverable error, or {@code null} if completed normally
357		*/
358	<	private void setSp(int s) {
359	<	_unsafe.putOrderedInt(this, spOffset, s);
358	>	protected void onTermination(Throwable exception) {
359	>	try {
360	>	stolen = null;
361	>	joining = null;
362	>	cancelTasks();
363	>	setTerminated();
364	>	pool.workerTerminated(this);
365	>	} catch (Throwable ex) {        // Shouldn't ever happen
366	>	if (exception == null)      // but if so, at least rethrown
367	>	exception = ex;
368	>	} finally {
369	>	if (exception != null)
370	>	UNSAFE.throwException(exception);
371	>	}
372		}
373
374		/**
375	<	* Add in store-order the given task at given slot of q to
376	<	* null. Caller must ensure q is nonnull and index is in range.
375	>	* This method is required to be public, but should never be
376	>	* called explicitly. It performs the main run loop to execute
377	>	* ForkJoinTasks.
378		*/
379	<	private static void setSlot(ForkJoinTask<?>[] q, int i,
380	<	ForkJoinTask<?> t){
381	<	_unsafe.putOrderedObject(q, (i << qShift) + qBase, t);
379	>	public void run() {
380	>	Throwable exception = null;
381	>	try {
382	>	onStart();
383	>	mainLoop();
384	>	} catch (Throwable ex) {
385	>	exception = ex;
386	>	} finally {
387	>	onTermination(exception);
388	>	}
389		}
390
391	+	// helpers for run()
392	+
393		/**
394	<	* CAS given slot of q to null. Caller must ensure q is nonnull
284	<	* and index is in range.
394	>	* Find and execute tasks and check status while running
395		*/
396	<	private static boolean casSlotNull(ForkJoinTask<?>[] q, int i,
397	<	ForkJoinTask<?> t) {
398	<	return _unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null);
396	>	private void mainLoop() {
397	>	boolean ran = false;      // true if ran task in last loop iter
398	>	boolean prevRan = false;  // true if ran on last or previous step
399	>	ForkJoinPool p = pool;
400	>	for (;;) {
401	>	p.preStep(this, prevRan);
402	>	if (runState != 0)
403	>	return;
404	>	ForkJoinTask<?> t; // try to get and run stolen or submitted task
405	>	if ((t = scan()) != null || (t = pollSubmission()) != null) {
406	>	t.tryExec();
407	>	if (base != sp)
408	>	runLocalTasks();
409	>	stolen = null;
410	>	prevRan = ran = true;
411	>	}
412	>	else {
413	>	prevRan = ran;
414	>	ran = false;
415	>	}
416	>	}
417		}
418
419	<	// Main queue methods
419	>	/**
420	>	* Runs local tasks until queue is empty or shut down.  Call only
421	>	* while active.
422	>	*/
423	>	private void runLocalTasks() {
424	>	while (runState == 0) {
425	>	ForkJoinTask<?> t = locallyFifo? locallyDeqTask() : popTask();
426	>	if (t != null)
427	>	t.tryExec();
428	>	else if (base == sp)
429	>	break;
430	>	}
431	>	}
432
433		/**
434	<	* Pushes a task. Called only by current thread.
435	<	* @param t the task. Caller must ensure nonnull
434	>	* If a submission exists, try to activate and take it
435	>	*
436	>	* @return a task, if available
437	>	*/
438	>	private ForkJoinTask<?> pollSubmission() {
439	>	ForkJoinPool p = pool;
440	>	while (p.hasQueuedSubmissions()) {
441	>	if (active || (active = p.tryIncrementActiveCount())) {
442	>	ForkJoinTask<?> t = p.pollSubmission();
443	>	return t != null ? t : scan(); // if missed, rescan
444	>	}
445	>	}
446	>	return null;
447	>	}
448	>
449	>	/*
450	>	* Intrinsics-based atomic writes for queue slots. These are
451	>	* basically the same as methods in AtomicObjectArray, but
452	>	* specialized for (1) ForkJoinTask elements (2) requirement that
453	>	* nullness and bounds checks have already been performed by
454	>	* callers and (3) effective offsets are known not to overflow
455	>	* from int to long (because of MAXIMUM_QUEUE_CAPACITY). We don't
456	>	* need corresponding version for reads: plain array reads are OK
457	>	* because they protected by other volatile reads and are
458	>	* confirmed by CASes.
459	>	*
460	>	* Most uses don't actually call these methods, but instead contain
461	>	* inlined forms that enable more predictable optimization.  We
462	>	* don't define the version of write used in pushTask at all, but
463	>	* instead inline there a store-fenced array slot write.
464	>	*/
465	>
466	>	/**
467	>	* CASes slot i of array q from t to null. Caller must ensure q is
468	>	* non-null and index is in range.
469	>	*/
470	>	private static final boolean casSlotNull(ForkJoinTask<?>[] q, int i,
471	>	ForkJoinTask<?> t) {
472	>	return UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null);
473	>	}
474	>
475	>	/**
476	>	* Performs a volatile write of the given task at given slot of
477	>	* array q.  Caller must ensure q is non-null and index is in
478	>	* range. This method is used only during resets and backouts.
479	>	*/
480	>	private static final void writeSlot(ForkJoinTask<?>[] q, int i,
481	>	ForkJoinTask<?> t) {
482	>	UNSAFE.putObjectVolatile(q, (i << qShift) + qBase, t);
483	>	}
484	>
485	>	// queue methods
486	>
487	>	/**
488	>	* Pushes a task. Call only from this thread.
489	>	*
490	>	* @param t the task. Caller must ensure non-null.
491		*/
492		final void pushTask(ForkJoinTask<?> t) {
493		ForkJoinTask<?>[] q = queue;
494	<	int mask = q.length - 1;
495	<	int s = sp;
496	<	_unsafe.putOrderedObject(q, ((s & mask) << qShift) + qBase, t);
497	<	_unsafe.putOrderedInt(this, spOffset, ++s);
498	<	if ((s -= base) == 1)
499	<	pool.signalNonEmptyWorkerQueue();
500	<	else if (s >= mask)
306	<	growQueue();
494	>	int mask = q.length - 1; // implicit assert q != null
495	>	int s = sp++;            // ok to increment sp before slot write
496	>	UNSAFE.putOrderedObject(q, ((s & mask) << qShift) + qBase, t);
497	>	if ((s -= base) == 0)
498	>	pool.signalWork();   // was empty
499	>	else if (s == mask)
500	>	growQueue();         // is full
501		}
502
503		/**
504		* Tries to take a task from the base of the queue, failing if
505	<	* either empty or contended.
506	<	* @return a task, or null if none or contended.
505	>	* empty or contended. Note: Specializations of this code appear
506	>	* in locallyDeqTask and elsewhere.
507	>	*
508	>	* @return a task, or null if none or contended
509		*/
510	<	private ForkJoinTask<?> deqTask() {
315	<	ForkJoinTask<?>[] q;
510	>	final ForkJoinTask<?> deqTask() {
511		ForkJoinTask<?> t;
512	<	int i;
513	<	int b;
514	<	if (sp != (b = base) &&
512	>	ForkJoinTask<?>[] q;
513	>	int b, i;
514	>	if ((b = base) != sp &&
515		(q = queue) != null && // must read q after b
516	<	(t = q[i = (q.length - 1) & b]) != null &&
517	<	_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) {
516	>	(t = q[i = (q.length - 1) & b]) != null && base == b &&
517	>	UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) {
518		base = b + 1;
519		return t;
520		}
#	Line 327 | Line 522 | public class ForkJoinWorkerThread extend
522		}
523
524		/**
525	<	* Returns a popped task, or null if empty.  Called only by
526	<	* current thread.
525	>	* Tries to take a task from the base of own queue. Assumes active
526	>	* status.  Called only by current thread.
527	>	*
528	>	* @return a task, or null if none
529		*/
530	<	final ForkJoinTask<?> popTask() {
334	<	ForkJoinTask<?> t;
335	<	int i;
530	>	final ForkJoinTask<?> locallyDeqTask() {
531		ForkJoinTask<?>[] q = queue;
532	<	int mask = q.length - 1;
533	<	int s = sp;
534	<	if (s != base &&
535	<	(t = q[i = (s - 1) & mask]) != null &&
536	<	_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) {
537	<	_unsafe.putOrderedInt(this, spOffset, s - 1);
538	<	return t;
532	>	if (q != null) {
533	>	ForkJoinTask<?> t;
534	>	int b, i;
535	>	while (sp != (b = base)) {
536	>	if ((t = q[i = (q.length - 1) & b]) != null && base == b &&
537	>	UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase,
538	>	t, null)) {
539	>	base = b + 1;
540	>	return t;
541	>	}
542	>	}
543		}
544		return null;
545		}
546
547		/**
548	<	* Specialized version of popTask to pop only if
549	<	* topmost element is the given task. Called only
550	<	* by current thread.
551	<	* @param t the task. Caller must ensure nonnull
548	>	* Returns a popped task, or null if empty. Assumes active status.
549	>	* Called only by current thread. (Note: a specialization of this
550	>	* code appears in popWhileJoining.)
551	>	*/
552	>	final ForkJoinTask<?> popTask() {
553	>	int s;
554	>	ForkJoinTask<?>[] q;
555	>	if (base != (s = sp) && (q = queue) != null) {
556	>	int i = (q.length - 1) & --s;
557	>	ForkJoinTask<?> t = q[i];
558	>	if (t != null && UNSAFE.compareAndSwapObject
559	>	(q, (i << qShift) + qBase, t, null)) {
560	>	sp = s;
561	>	return t;
562	>	}
563	>	}
564	>	return null;
565	>	}
566	>
567	>	/**
568	>	* Specialized version of popTask to pop only if topmost element
569	>	* is the given task. Called only by current thread while
570	>	* active.
571	>	*
572	>	* @param t the task. Caller must ensure non-null.
573		*/
574		final boolean unpushTask(ForkJoinTask<?> t) {
575	<	ForkJoinTask<?>[] q = queue;
576	<	int mask = q.length - 1;
577	<	int s = sp - 1;
578	<	if (_unsafe.compareAndSwapObject(q, ((s & mask) << qShift) + qBase,
579	<	t, null)) {
580	<	_unsafe.putOrderedInt(this, spOffset, s);
575	>	int s;
576	>	ForkJoinTask<?>[] q;
577	>	if (base != (s = sp) && (q = queue) != null &&
578	>	UNSAFE.compareAndSwapObject
579	>	(q, (((q.length - 1) & --s) << qShift) + qBase, t, null)) {
580	>	sp = s;
581		return true;
582		}
583		return false;
584		}
585
586		/**
587	<	* Returns next task to pop.
587	>	* Returns next task or null if empty or contended
588		*/
589	<	private ForkJoinTask<?> peekTask() {
589	>	final ForkJoinTask<?> peekTask() {
590		ForkJoinTask<?>[] q = queue;
591	<	return q == null? null : q[(sp - 1) & (q.length - 1)];
591	>	if (q == null)
592	>	return null;
593	>	int mask = q.length - 1;
594	>	int i = locallyFifo ? base : (sp - 1);
595	>	return q[i & mask];
596		}
597
598		/**
#	Line 393 | Line 617 | public class ForkJoinWorkerThread extend
617		ForkJoinTask<?> t = oldQ[oldIndex];
618		if (t != null && !casSlotNull(oldQ, oldIndex, t))
619		t = null;
620	<	setSlot(newQ, b & newMask, t);
620	>	writeSlot(newQ, b & newMask, t);
621		} while (++b != bf);
622	<	pool.signalIdleWorkers(false);
622	>	pool.signalWork();
623		}
624
401	–	// Runstate management
402	–
403	–	final boolean isShutdown()    { return runState >= SHUTDOWN;  }
404	–	final boolean isTerminating() { return runState >= TERMINATING;  }
405	–	final boolean isTerminated()  { return runState == TERMINATED; }
406	–	final boolean shutdown()      { return transitionRunStateTo(SHUTDOWN); }
407	–	final boolean shutdownNow()   { return transitionRunStateTo(TERMINATING); }
408	–
625		/**
626	<	* Transition to at least the given state. Return true if not
627	<	* already at least given state.
626	>	* Computes next value for random victim probe in scan().  Scans
627	>	* don't require a very high quality generator, but also not a
628	>	* crummy one.  Marsaglia xor-shift is cheap and works well enough.
629	>	* Note: This is manually inlined in scan()
630		*/
631	<	private boolean transitionRunStateTo(int state) {
632	<	for (;;) {
633	<	int s = runState;
634	<	if (s >= state)
417	<	return false;
418	<	if (_unsafe.compareAndSwapInt(this, runStateOffset, s, state))
419	<	return true;
420	<	}
631	>	private static final int xorShift(int r) {
632	>	r ^= r << 13;
633	>	r ^= r >>> 17;
634	>	return r ^ (r << 5);
635		}
636
637		/**
638	<	* Ensure status is active and if necessary adjust pool active count
638	>	* Tries to steal a task from another worker. Starts at a random
639	>	* index of workers array, and probes workers until finding one
640	>	* with non-empty queue or finding that all are empty.  It
641	>	* randomly selects the first n probes. If these are empty, it
642	>	* resorts to a circular sweep, which is necessary to accurately
643	>	* set active status. (The circular sweep uses steps of
644	>	* approximately half the array size plus 1, to avoid bias
645	>	* stemming from leftmost packing of the array in ForkJoinPool.)
646	>	*
647	>	* This method must be both fast and quiet -- usually avoiding
648	>	* memory accesses that could disrupt cache sharing etc other than
649	>	* those needed to check for and take tasks (or to activate if not
650	>	* already active). This accounts for, among other things,
651	>	* updating random seed in place without storing it until exit.
652	>	*
653	>	* @return a task, or null if none found
654		*/
655	<	final void activate() {
656	<	if (!active) {
657	<	active = true;
658	<	pool.incrementActiveCount();
655	>	private ForkJoinTask<?> scan() {
656	>	ForkJoinPool p = pool;
657	>	ForkJoinWorkerThread[] ws;        // worker array
658	>	int n;                            // upper bound of #workers
659	>	if ((ws = p.workers) != null && (n = ws.length) > 1) {
660	>	boolean canSteal = active;    // shadow active status
661	>	int r = seed;                 // extract seed once
662	>	int mask = n - 1;
663	>	int j = -n;                   // loop counter
664	>	int k = r;                    // worker index, random if j < 0
665	>	for (;;) {
666	>	ForkJoinWorkerThread v = ws[k & mask];
667	>	r ^= r << 13; r ^= r >>> 17; r ^= r << 5; // inline xorshift
668	>	if (v != null && v.base != v.sp) {
669	>	if (canSteal ||       // ensure active status
670	>	(canSteal = active = p.tryIncrementActiveCount())) {
671	>	int b = v.base;   // inline specialized deqTask
672	>	ForkJoinTask<?>[] q;
673	>	if (b != v.sp && (q = v.queue) != null) {
674	>	ForkJoinTask<?> t;
675	>	int i = (q.length - 1) & b;
676	>	long u = (i << qShift) + qBase; // raw offset
677	>	if ((t = q[i]) != null && v.base == b &&
678	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
679	>	stolen = t;
680	>	v.base = b + 1;
681	>	seed = r;
682	>	++stealCount;
683	>	return t;
684	>	}
685	>	}
686	>	}
687	>	j = -n;
688	>	k = r;                // restart on contention
689	>	}
690	>	else if (++j <= 0)
691	>	k = r;
692	>	else if (j <= n)
693	>	k += (n >>> 1) | 1;
694	>	else
695	>	break;
696	>	}
697		}
698	+	return null;
699		}
700
701	+	// Run State management
702	+
703	+	// status check methods used mainly by ForkJoinPool
704	+	final boolean isTerminating() { return (runState & TERMINATING) != 0; }
705	+	final boolean isTerminated()  { return (runState & TERMINATED) != 0; }
706	+	final boolean isSuspended()   { return (runState & SUSPENDED) != 0; }
707	+	final boolean isTrimmed()     { return (runState & TRIMMED) != 0; }
708	+
709		/**
710	<	* Ensure status is inactive and if necessary adjust pool active count
710	>	* Sets state to TERMINATING, also resuming if suspended.
711		*/
712	<	final void inactivate() {
713	<	if (active) {
714	<	active = false;
715	<	pool.decrementActiveCount();
712	>	final void shutdown() {
713	>	for (;;) {
714	>	int s = runState;
715	>	if ((s & SUSPENDED) != 0) { // kill and wakeup if suspended
716	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
717	>	(s & ~SUSPENDED) |
718	>	(TRIMMED|TERMINATING))) {
719	>	LockSupport.unpark(this);
720	>	break;
721	>	}
722	>	}
723	>	else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
724	>	s | TERMINATING))
725	>	break;
726		}
727		}
728
443	–	// Lifecycle methods
444	–
729		/**
730	<	* Initializes internal state after construction but before
447	<	* processing any tasks. If you override this method, you must
448	<	* invoke super.onStart() at the beginning of the method.
449	<	* Initialization requires care: Most fields must have legal
450	<	* default values, to ensure that attempted accesses from other
451	<	* threads work correctly even before this thread starts
452	<	* processing tasks.
730	>	* Sets state to TERMINATED. Called only by this thread.
731		*/
732	<	protected void onStart() {
733	<	juRandomSeed = randomSeedGenerator.nextLong();
734	<	do;while((randomVictimSeed = nextRandomInt()) == 0); // must be nonzero
735	<	if (queue == null)
736	<	queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY];
732	>	private void setTerminated() {
733	>	int s;
734	>	do {} while (!UNSAFE.compareAndSwapInt(this, runStateOffset,
735	>	s = runState,
736	>	s | (TERMINATING|TERMINATED)));
737	>	}
738
739	<	// Heuristically allow one initial thread to warm up; others wait
740	<	if (poolIndex < pool.getParallelism() - 1) {
741	<	eventCount = pool.sync(this, 0);
742	<	activate();
743	<	}
739	>	/**
740	>	* Instrumented version of park used by ForkJoinPool.awaitEvent
741	>	*/
742	>	final void doPark() {
743	>	++parkCount;
744	>	LockSupport.park(this);
745		}
746
747		/**
748	<	* Perform cleanup associated with termination of this worker
749	<	* thread.  If you override this method, you must invoke
470	<	* super.onTermination at the end of the overridden method.
748	>	* If suspended, tries to set status to unsuspended.
749	>	* Caller must unpark to actually resume
750		*
751	<	* @param exception the exception causing this thread to abort due
473	<	* to an unrecoverable error, or null if completed normally.
751	>	* @return true if successful
752		*/
753	<	protected void onTermination(Throwable exception) {
754	<	try {
755	<	clearLocalTasks();
756	<	inactivate();
757	<	cancelTasks();
758	<	} finally {
481	<	terminate(exception);
482	<	}
753	>	final boolean tryUnsuspend() {
754	>	int s = runState;
755	>	if ((s & SUSPENDED) != 0)
756	>	return UNSAFE.compareAndSwapInt(this, runStateOffset, s,
757	>	s & ~SUSPENDED);
758	>	return false;
759		}
760
761		/**
762	<	* Notify pool of termination and, if exception is nonnull,
763	<	* rethrow it to trigger this thread's uncaughtExceptionHandler
762	>	* Sets suspended status and blocks as spare until resumed,
763	>	* shutdown, or timed out.
764	>	*
765	>	* @return false if trimmed
766		*/
767	<	private void terminate(Throwable exception) {
768	<	transitionRunStateTo(TERMINATED);
769	<	try {
770	<	pool.workerTerminated(this);
771	<	} finally {
772	<	if (exception != null)
773	<	ForkJoinTask.rethrowException(exception);
767	>	final boolean suspendAsSpare() {
768	>	for (;;) {               // set suspended unless terminating
769	>	int s = runState;
770	>	if ((s & TERMINATING) != 0) { // must kill
771	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
772	>	s | (TRIMMED | TERMINATING)))
773	>	return false;
774	>	}
775	>	else if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
776	>	s | SUSPENDED))
777	>	break;
778	>	}
779	>	boolean timed;
780	>	long nanos;
781	>	long startTime;
782	>	if (poolIndex < pool.parallelism) {
783	>	timed = false;
784	>	nanos = 0L;
785	>	startTime = 0L;
786	>	}
787	>	else {
788	>	timed = true;
789	>	nanos = SPARE_KEEPALIVE_NANOS;
790	>	startTime = System.nanoTime();
791	>	}
792	>	pool.accumulateStealCount(this);
793	>	lastEventCount = 0;      // reset upon resume
794	>	interrupted();           // clear/ignore interrupts
795	>	while ((runState & SUSPENDED) != 0) {
796	>	++parkCount;
797	>	if (!timed)
798	>	LockSupport.park(this);
799	>	else if ((nanos -= (System.nanoTime() - startTime)) > 0)
800	>	LockSupport.parkNanos(this, nanos);
801	>	else { // try to trim on timeout
802	>	int s = runState;
803	>	if (UNSAFE.compareAndSwapInt(this, runStateOffset, s,
804	>	(s & ~SUSPENDED) |
805	>	(TRIMMED|TERMINATING)))
806	>	return false;
807	>	}
808		}
809	+	return true;
810		}
811
812	+	// Misc support methods for ForkJoinPool
813	+
814		/**
815	<	* Run local tasks on exit from main.
815	>	* Returns an estimate of the number of tasks in the queue.  Also
816	>	* used by ForkJoinTask.
817		*/
818	<	private void clearLocalTasks() {
819	<	while (base != sp && !pool.isTerminating()) {
504	<	ForkJoinTask<?> t = popTask();
505	<	if (t != null) {
506	<	activate(); // ensure active status
507	<	t.quietlyExec();
508	<	}
509	<	}
818	>	final int getQueueSize() {
819	>	return -base + sp;
820		}
821
822		/**
#	Line 517 | Line 827 | public class ForkJoinWorkerThread extend
827		while (base != sp) {
828		ForkJoinTask<?> t = deqTask();
829		if (t != null)
830	<	t.cancelIgnoreExceptions();
521	<	}
522	<	}
523	<
524	<	/**
525	<	* This method is required to be public, but should never be
526	<	* called explicitly. It performs the main run loop to execute
527	<	* ForkJoinTasks.
528	<	*/
529	<	public void run() {
530	<	Throwable exception = null;
531	<	try {
532	<	onStart();
533	<	while (!isShutdown())
534	<	step();
535	<	} catch (Throwable ex) {
536	<	exception = ex;
537	<	} finally {
538	<	onTermination(exception);
830	>	t.cancelIgnoringExceptions();
831		}
832		}
833
834		/**
835	<	* Main top-level action.
835	>	* Drains tasks to given collection c.
836	>	*
837	>	* @return the number of tasks drained
838		*/
839	<	private void step() {
840	<	ForkJoinTask<?> t = sp != base? popTask() : null;
841	<	if (t != null || (t = scan(null, true)) != null) {
842	<	activate();
843	<	t.quietlyExec();
844	<	}
845	<	else {
846	<	inactivate();
553	<	eventCount = pool.sync(this, eventCount);
839	>	final int drainTasksTo(Collection<? super ForkJoinTask<?>> c) {
840	>	int n = 0;
841	>	while (base != sp) {
842	>	ForkJoinTask<?> t = deqTask();
843	>	if (t != null) {
844	>	c.add(t);
845	>	++n;
846	>	}
847		}
848	+	return n;
849		}
850
851	<	// scanning for and stealing tasks
851	>	// Support methods for ForkJoinTask
852
853		/**
854	<	* Computes next value for random victim probe. Scans don't
561	<	* require a very high quality generator, but also not a crummy
562	<	* one. Marsaglia xor-shift is cheap and works well.
854	>	* Possibly runs some tasks and/or blocks, until task is done.
855		*
856	<	* This is currently unused, and manually inlined
856	>	* @param joinMe the task to join
857		*/
858	<	private static int xorShift(int r) {
859	<	r ^= r << 1;
860	<	r ^= r >>> 3;
861	<	r ^= r << 10;
862	<	return r;
858	>	final void joinTask(ForkJoinTask<?> joinMe) {
859	>	ForkJoinTask<?> prevJoining = joining;
860	>	joining = joinMe;
861	>	while (joinMe.status >= 0) {
862	>	int s = sp;
863	>	if (s == base) {
864	>	nonlocalJoinTask(joinMe);
865	>	break;
866	>	}
867	>	// process local task
868	>	ForkJoinTask<?> t;
869	>	ForkJoinTask<?>[] q = queue;
870	>	int i = (q.length - 1) & --s;
871	>	long u = (i << qShift) + qBase; // raw offset
872	>	if ((t = q[i]) != null &&
873	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
874	>	/*
875	>	* This recheck (and similarly in nonlocalJoinTask)
876	>	* handles cases where joinMe is independently
877	>	* cancelled or forced even though there is other work
878	>	* available. Back out of the pop by putting t back
879	>	* into slot before we commit by setting sp.
880	>	*/
881	>	if (joinMe.status < 0) {
882	>	UNSAFE.putObjectVolatile(q, u, t);
883	>	break;
884	>	}
885	>	sp = s;
886	>	t.tryExec();
887	>	}
888	>	}
889	>	joining = prevJoining;
890		}
891
892		/**
893	<	* Tries to steal a task from another worker and/or, if enabled,
894	<	* submission queue. Starts at a random index of workers array,
895	<	* and probes workers until finding one with non-empty queue or
896	<	* finding that all are empty.  It randomly selects the first n-1
897	<	* probes. If these are empty, it resorts to full circular
898	<	* traversal, which is necessary to accurately set active status
899	<	* by caller. Also restarts if pool barrier has tripped since last
900	<	* scan, which forces refresh of workers array, in case barrier
901	<	* was associated with resize.
902	<	*
584	<	* This method must be both fast and quiet -- usually avoiding
585	<	* memory accesses that could disrupt cache sharing etc other than
586	<	* those needed to check for and take tasks. This accounts for,
587	<	* among other things, updating random seed in place without
588	<	* storing it until exit. (Note that we only need to store it if
589	<	* we found a task; otherwise it doesn't matter if we start at the
590	<	* same place next time.)
893	>	* Tries to locate and help perform tasks for a stealer of the
894	>	* given task (or in turn one of its stealers), blocking (via
895	>	* pool.tryAwaitJoin) upon failure to find work.  Traces
896	>	* stolen->joining links looking for a thread working on
897	>	* a descendant of the given task and with a non-empty queue to
898	>	* steal back and execute tasks from. Inhibits mutual steal chains
899	>	* and scans on outer joins upon nesting to avoid unbounded
900	>	* growth.  Restarts search upon encountering inconsistencies.
901	>	* Tries to block if two passes agree that there are no remaining
902	>	* targets.
903		*
904	<	* @param joinMe if non null; exit early if done
593	<	* @param checkSubmissions true if OK to take submissions
594	<	* @return a task, or null if none found
904	>	* @param joinMe the task to join
905		*/
906	<	private ForkJoinTask<?> scan(ForkJoinTask<?> joinMe,
597	<	boolean checkSubmissions) {
906	>	private void nonlocalJoinTask(ForkJoinTask<?> joinMe) {
907		ForkJoinPool p = pool;
908	<	if (p == null)                    // Never null, but avoids
909	<	return null;                  //   implicit nullchecks below
910	<	int r = randomVictimSeed;         // extract once to keep scan quiet
911	<	restart:                          // outer loop refreshes ws array
912	<	while (joinMe == null || joinMe.status >= 0) {
913	<	int mask;
914	<	ForkJoinWorkerThread[] ws = p.workers;
915	<	if (ws != null && (mask = ws.length - 1) > 0) {
916	<	int probes = -mask;       // use random index while negative
917	<	int idx = r;
918	<	for (;;) {
919	<	ForkJoinWorkerThread v;
920	<	// inlined xorshift to update seed
921	<	r ^= r << 1;  r ^= r >>> 3; r ^= r << 10;
922	<	if ((v = ws[mask & idx]) != null && v.sp != v.base) {
923	<	ForkJoinTask<?> t;
924	<	activate();
925	<	if ((joinMe == null || joinMe.status >= 0) &&
926	<	(t = v.deqTask()) != null) {
927	<	randomVictimSeed = r;
928	<	++stealCount;
929	<	return t;
908	>	int scans = p.parallelism;       // give up if too many retries
909	>	ForkJoinTask<?> bottom = null;   // target seen when can't descend
910	>	restart: while (joinMe.status >= 0) {
911	>	ForkJoinTask<?> target = null;
912	>	ForkJoinTask<?> next = joinMe;
913	>	while (scans >= 0 && next != null) {
914	>	--scans;
915	>	target = next;
916	>	next = null;
917	>	ForkJoinWorkerThread v = null;
918	>	ForkJoinWorkerThread[] ws = p.workers;
919	>	int n = ws.length;
920	>	for (int j = 0; j < n; ++j) {
921	>	ForkJoinWorkerThread w = ws[j];
922	>	if (w != null && w.stolen == target) {
923	>	v = w;
924	>	break;
925	>	}
926	>	}
927	>	if (v != null && v != this) {
928	>	ForkJoinTask<?> prevStolen = stolen;
929	>	int b;
930	>	ForkJoinTask<?>[] q;
931	>	while ((b = v.base) != v.sp && (q = v.queue) != null) {
932	>	int i = (q.length - 1) & b;
933	>	long u = (i << qShift) + qBase;
934	>	ForkJoinTask<?> t = q[i];
935	>	if (target.status < 0)
936	>	continue restart;
937	>	if (t != null && v.base == b &&
938	>	UNSAFE.compareAndSwapObject(q, u, t, null)) {
939	>	if (joinMe.status < 0) {
940	>	UNSAFE.putObjectVolatile(q, u, t);
941	>	return; // back out
942	>	}
943	>	stolen = t;
944	>	v.base = b + 1;
945	>	t.tryExec();
946	>	stolen = prevStolen;
947		}
948	<	continue restart; // restart on contention
948	>	if (joinMe.status < 0)
949	>	return;
950		}
951	<	if ((probes >> 1) <= mask) // n-1 random then circular
625	<	idx = (probes++ < 0)? r : (idx + 1);
626	<	else
627	<	break;
951	>	next = v.joining;
952		}
953	+	if (target.status < 0)
954	+	continue restart;  // inconsistent
955	+	if (joinMe.status < 0)
956	+	return;
957		}
630	–	if (checkSubmissions && p.hasQueuedSubmissions()) {
631	–	activate();
632	–	ForkJoinTask<?> t = p.pollSubmission();
633	–	if (t != null)
634	–	return t;
635	–	}
636	–	else {
637	–	long ec = eventCount;     // restart on pool event
638	–	if ((eventCount = p.getEventCount()) == ec)
639	–	break;
640	–	}
641	–	}
642	–	return null;
643	–	}
644	–
645	–	/**
646	–	* Callback from pool.sync to rescan before blocking.  If a
647	–	* task is found, it is pushed so it can be executed upon return.
648	–	* @return true if found and pushed a task
649	–	*/
650	–	final boolean prescan() {
651	–	ForkJoinTask<?> t = scan(null, true);
652	–	if (t != null) {
653	–	pushTask(t);
654	–	return true;
655	–	}
656	–	else {
657	–	inactivate();
658	–	return false;
659	–	}
660	–	}
958
959	<	/**
960	<	* Implements ForkJoinTask.helpJoin
961	<	*/
962	<	final int helpJoinTask(ForkJoinTask<?> joinMe) {
963	<	ForkJoinTask<?> t = null;
667	<	int s;
668	<	while ((s = joinMe.status) >= 0) {
669	<	if (t == null) {
670	<	if ((t = scan(joinMe, false)) == null)  // block if no work
671	<	return joinMe.awaitDone(this, false);
672	<	// else recheck status before exec
673	<	}
674	<	else {
675	<	t.quietlyExec();
676	<	t = null;
677	<	}
959	>	if (bottom != target)
960	>	bottom = target;    // recheck landing spot
961	>	else if (p.tryAwaitJoin(joinMe) < 0)
962	>	return;             // successfully blocked
963	>	Thread.yield();         // tame spin in case too many active
964		}
679	–	if (t != null) // unsteal
680	–	pushTask(t);
681	–	return s;
965		}
966
684	–	// Support for public static and/or ForkJoinTask methods
685	–
967		/**
968	<	* Returns an estimate of the number of tasks in the queue.
969	<	*/
970	<	final int getQueueSize() {
971	<	int b = base;
972	<	int n = sp - b;
973	<	return n <= 0? 0 : n; // suppress momentarily negative values
974	<	}
975	<
976	<	/**
977	<	* Runs one popped task, if available
978	<	* @return true if ran a task
968	>	* Returns an estimate of the number of tasks, offset by a
969	>	* function of number of idle workers.
970	>	*
971	>	* This method provides a cheap heuristic guide for task
972	>	* partitioning when programmers, frameworks, tools, or languages
973	>	* have little or no idea about task granularity.  In essence by
974	>	* offering this method, we ask users only about tradeoffs in
975	>	* overhead vs expected throughput and its variance, rather than
976	>	* how finely to partition tasks.
977	>	*
978	>	* In a steady state strict (tree-structured) computation, each
979	>	* thread makes available for stealing enough tasks for other
980	>	* threads to remain active. Inductively, if all threads play by
981	>	* the same rules, each thread should make available only a
982	>	* constant number of tasks.
983	>	*
984	>	* The minimum useful constant is just 1. But using a value of 1
985	>	* would require immediate replenishment upon each steal to
986	>	* maintain enough tasks, which is infeasible.  Further,
987	>	* partitionings/granularities of offered tasks should minimize
988	>	* steal rates, which in general means that threads nearer the top
989	>	* of computation tree should generate more than those nearer the
990	>	* bottom. In perfect steady state, each thread is at
991	>	* approximately the same level of computation tree. However,
992	>	* producing extra tasks amortizes the uncertainty of progress and
993	>	* diffusion assumptions.
994	>	*
995	>	* So, users will want to use values larger, but not much larger
996	>	* than 1 to both smooth over transient shortages and hedge
997	>	* against uneven progress; as traded off against the cost of
998	>	* extra task overhead. We leave the user to pick a threshold
999	>	* value to compare with the results of this call to guide
1000	>	* decisions, but recommend values such as 3.
1001	>	*
1002	>	* When all threads are active, it is on average OK to estimate
1003	>	* surplus strictly locally. In steady-state, if one thread is
1004	>	* maintaining say 2 surplus tasks, then so are others. So we can
1005	>	* just use estimated queue length (although note that (sp - base)
1006	>	* can be an overestimate because of stealers lagging increments
1007	>	* of base).  However, this strategy alone leads to serious
1008	>	* mis-estimates in some non-steady-state conditions (ramp-up,
1009	>	* ramp-down, other stalls). We can detect many of these by
1010	>	* further considering the number of "idle" threads, that are
1011	>	* known to have zero queued tasks, so compensate by a factor of
1012	>	* (#idle/#active) threads.
1013		*/
1014	<	private boolean runLocalTask() {
1015	<	ForkJoinTask<?> t = popTask();
701	<	if (t == null)
702	<	return false;
703	<	t.quietlyExec();
704	<	return true;
1014	>	final int getEstimatedSurplusTaskCount() {
1015	>	return sp - base - pool.idlePerActive();
1016		}
1017
1018		/**
1019	<	* Pops or steals a task
1020	<	* @return task, or null if none available
1019	>	* Gets and removes a local task.
1020	>	*
1021	>	* @return a task, if available
1022		*/
1023	<	private ForkJoinTask<?> getLocalOrStolenTask() {
1024	<	ForkJoinTask<?> t = popTask();
1025	<	return t != null? t : scan(null, false);
1023	>	final ForkJoinTask<?> pollLocalTask() {
1024	>	while (sp != base) {
1025	>	if (active || (active = pool.tryIncrementActiveCount()))
1026	>	return locallyFifo? locallyDeqTask() : popTask();
1027	>	}
1028	>	return null;
1029		}
1030
1031		/**
1032	<	* Runs a popped or stolen task, if available
1033	<	* @return true if ran a task
1032	>	* Gets and removes a local or stolen task.
1033	>	*
1034	>	* @return a task, if available
1035		*/
1036	<	private boolean runLocalOrStolenTask() {
1037	<	ForkJoinTask<?> t = getLocalOrStolenTask();
1038	<	if (t == null)
723	<	return false;
724	<	t.quietlyExec();
725	<	return true;
1036	>	final ForkJoinTask<?> pollTask() {
1037	>	ForkJoinTask<?> t;
1038	>	return (t = pollLocalTask()) != null ? t : scan();
1039		}
1040
1041		/**
1042	<	* Runs tasks until pool isQuiescent
1042	>	* Runs tasks until {@code pool.isQuiescent()}.
1043		*/
1044		final void helpQuiescePool() {
732	–	activate();
1045		for (;;) {
1046	<	if (!runLocalOrStolenTask()) {
1047	<	inactivate();
1048	<	if (pool.isQuiescent()) {
1049	<	activate(); // re-activate on exit
1050	<	break;
1046	>	ForkJoinTask<?> t = pollLocalTask();
1047	>	if (t != null || (t = scan()) != null) {
1048	>	t.tryExec();
1049	>	stolen = null;
1050	>	}
1051	>	else {
1052	>	ForkJoinPool p = pool;
1053	>	if (active) {
1054	>	active = false; // inactivate
1055	>	do {} while (!p.tryDecrementActiveCount());
1056	>	}
1057	>	if (p.isQuiescent()) {
1058	>	active = true; // re-activate
1059	>	do {} while (!p.tryIncrementActiveCount());
1060	>	return;
1061		}
1062		}
1063		}
1064		}
1065
1066	<	/**
745	<	* Returns an estimate of the number of tasks, offset by a
746	<	* function of number of idle workers.
747	<	*/
748	<	final int getEstimatedSurplusTaskCount() {
749	<	return (sp - base) - (pool.getIdleThreadCount() >>> 1);
750	<	}
751	<
752	<	// Public methods on current thread
753	<
754	<	/**
755	<	* Returns the pool hosting the current task execution.
756	<	* @return the pool
757	<	*/
758	<	public static ForkJoinPool getPool() {
759	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pool;
760	<	}
761	<
762	<	/**
763	<	* Returns the index number of the current worker thread in its
764	<	* pool.  The returned value ranges from zero to the maximum
765	<	* number of threads (minus one) that have ever been created in
766	<	* the pool.  This method may be useful for applications that
767	<	* track status or collect results per-worker rather than
768	<	* per-task.
769	<	* @return the index number.
770	<	*/
771	<	public static int getPoolIndex() {
772	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).poolIndex;
773	<	}
774	<
775	<	/**
776	<	* Returns an estimate of the number of tasks waiting to be run by
777	<	* the current worker thread. This value may be useful for
778	<	* heuristic decisions about whether to fork other tasks.
779	<	* @return the number of tasks
780	<	*/
781	<	public static int getLocalQueueSize() {
782	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
783	<	getQueueSize();
784	<	}
1066	>	// Unsafe mechanics
1067
1068	<	/**
1069	<	* Returns, but does not remove or execute, the next task locally
1070	<	* queued for execution by the current worker thread. There is no
1071	<	* guarantee that this task will be the next one actually returned
1072	<	* or executed from other polling or execution methods.
1073	<	* @return the next task or null if none
792	<	*/
793	<	public static ForkJoinTask<?> peekLocalTask() {
794	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
795	<	}
796	<
797	<	/**
798	<	* Removes and returns, without executing, the next task queued
799	<	* for execution in the current worker thread's local queue.
800	<	* @return the next task to execute, or null if none
801	<	*/
802	<	public static ForkJoinTask<?> pollLocalTask() {
803	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask();
804	<	}
805	<
806	<	/**
807	<	* Execute the next task locally queued by the current worker, if
808	<	* one is available.
809	<	* @return true if a task was run; a false return indicates
810	<	* that no task was available.
811	<	*/
812	<	public static boolean executeLocalTask() {
813	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
814	<	runLocalTask();
815	<	}
1068	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1069	>	private static final long runStateOffset =
1070	>	objectFieldOffset("runState", ForkJoinWorkerThread.class);
1071	>	private static final long qBase =
1072	>	UNSAFE.arrayBaseOffset(ForkJoinTask[].class);
1073	>	private static final int qShift;
1074
1075	<	/**
1076	<	* Removes and returns, without executing, the next task queued
1077	<	* for execution in the current worker thread's local queue or if
1078	<	* none, a task stolen from another worker, if one is available.
1079	<	* A null return does not necessarily imply that all tasks are
822	<	* completed, only that there are currently none available.
823	<	* @return the next task to execute, or null if none
824	<	*/
825	<	public static ForkJoinTask<?> pollTask() {
826	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
827	<	getLocalOrStolenTask();
828	<	}
829	<
830	<	/**
831	<	* Helps this program complete by processing a local or stolen
832	<	* task, if one is available.  This method may be useful when
833	<	* several tasks are forked, and only one of them must be joined,
834	<	* as in:
835	<	*
836	<	* <pre>
837	<	*   while (!t1.isDone() &amp;&amp; !t2.isDone())
838	<	*     ForkJoinWorkerThread.executeTask();
839	<	* </pre>
840	<	*
841	<	* @return true if a task was run; a false return indicates
842	<	* that no task was available.
843	<	*/
844	<	public static boolean executeTask() {
845	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
846	<	runLocalOrStolenTask();
847	<	}
848	<
849	<	// Per-worker exported random numbers
850	<
851	<	// Same constants as java.util.Random
852	<	final static long JURandomMultiplier = 0x5DEECE66DL;
853	<	final static long JURandomAddend = 0xBL;
854	<	final static long JURandomMask = (1L << 48) - 1;
855	<
856	<	private final int nextJURandom(int bits) {
857	<	long next = (juRandomSeed * JURandomMultiplier + JURandomAddend) &
858	<	JURandomMask;
859	<	juRandomSeed = next;
860	<	return (int)(next >>> (48 - bits));
861	<	}
862	<
863	<	private final int nextJURandomInt(int n) {
864	<	if (n <= 0)
865	<	throw new IllegalArgumentException("n must be positive");
866	<	int bits = nextJURandom(31);
867	<	if ((n & -n) == n)
868	<	return (int)((n * (long)bits) >> 31);
869	<
870	<	for (;;) {
871	<	int val = bits % n;
872	<	if (bits - val + (n-1) >= 0)
873	<	return val;
874	<	bits = nextJURandom(31);
875	<	}
876	<	}
877	<
878	<	private final long nextJURandomLong() {
879	<	return ((long)(nextJURandom(32)) << 32) + nextJURandom(32);
1075	>	static {
1076	>	int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class);
1077	>	if ((s & (s-1)) != 0)
1078	>	throw new Error("data type scale not a power of two");
1079	>	qShift = 31 - Integer.numberOfLeadingZeros(s);
1080		}
1081
1082	<	private final long nextJURandomLong(long n) {
1083	<	if (n <= 0)
1084	<	throw new IllegalArgumentException("n must be positive");
1085	<	long offset = 0;
1086	<	while (n >= Integer.MAX_VALUE) { // randomly pick half range
1087	<	int bits = nextJURandom(2); // 2nd bit for odd vs even split
1088	<	long half = n >>> 1;
1089	<	long nextn = ((bits & 2) == 0)? half : n - half;
890	<	if ((bits & 1) == 0)
891	<	offset += n - nextn;
892	<	n = nextn;
1082	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1083	>	try {
1084	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1085	>	} catch (NoSuchFieldException e) {
1086	>	// Convert Exception to corresponding Error
1087	>	NoSuchFieldError error = new NoSuchFieldError(field);
1088	>	error.initCause(e);
1089	>	throw error;
1090		}
894	–	return offset + nextJURandomInt((int)n);
895	–	}
896	–
897	–	private final double nextJURandomDouble() {
898	–	return (((long)(nextJURandom(26)) << 27) + nextJURandom(27))
899	–	/ (double)(1L << 53);
1091		}
1092
1093		/**
1094	<	* Returns a random integer using a per-worker random
1095	<	* number generator with the same properties as
1096	<	* {@link java.util.Random#nextInt}
1097	<	* @return the next pseudorandom, uniformly distributed {@code int}
1098	<	*         value from this worker's random number generator's sequence
908	<	*/
909	<	public static int nextRandomInt() {
910	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
911	<	nextJURandom(32);
912	<	}
913	<
914	<	/**
915	<	* Returns a random integer using a per-worker random
916	<	* number generator with the same properties as
917	<	* {@link java.util.Random#nextInt(int)}
918	<	* @param n the bound on the random number to be returned.  Must be
919	<	*        positive.
920	<	* @return the next pseudorandom, uniformly distributed {@code int}
921	<	*         value between {@code 0} (inclusive) and {@code n} (exclusive)
922	<	*         from this worker's random number generator's sequence
923	<	* @throws IllegalArgumentException if n is not positive
924	<	*/
925	<	public static int nextRandomInt(int n) {
926	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
927	<	nextJURandomInt(n);
928	<	}
929	<
930	<	/**
931	<	* Returns a random long using a per-worker random
932	<	* number generator with the same properties as
933	<	* {@link java.util.Random#nextLong}
934	<	* @return the next pseudorandom, uniformly distributed {@code long}
935	<	*         value from this worker's random number generator's sequence
936	<	*/
937	<	public static long nextRandomLong() {
938	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
939	<	nextJURandomLong();
940	<	}
941	<
942	<	/**
943	<	* Returns a random integer using a per-worker random
944	<	* number generator with the same properties as
945	<	* {@link java.util.Random#nextInt(int)}
946	<	* @param n the bound on the random number to be returned.  Must be
947	<	*        positive.
948	<	* @return the next pseudorandom, uniformly distributed {@code int}
949	<	*         value between {@code 0} (inclusive) and {@code n} (exclusive)
950	<	*         from this worker's random number generator's sequence
951	<	* @throws IllegalArgumentException if n is not positive
952	<	*/
953	<	public static long nextRandomLong(long n) {
954	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
955	<	nextJURandomLong(n);
956	<	}
957	<
958	<	/**
959	<	* Returns a random double using a per-worker random
960	<	* number generator with the same properties as
961	<	* {@link java.util.Random#nextDouble}
962	<	* @return the next pseudorandom, uniformly distributed {@code double}
963	<	*         value between {@code 0.0} and {@code 1.0} from this
964	<	*         worker's random number generator's sequence
1094	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1095	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1096	>	* into a jdk.
1097	>	*
1098	>	* @return a sun.misc.Unsafe
1099		*/
1100	<	public static double nextRandomDouble() {
967	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
968	<	nextJURandomDouble();
969	<	}
970	<
971	<	// Temporary Unsafe mechanics for preliminary release
972	<
973	<	static final Unsafe _unsafe;
974	<	static final long baseOffset;
975	<	static final long spOffset;
976	<	static final long qBase;
977	<	static final int qShift;
978	<	static final long runStateOffset;
979	<	static {
1100	>	private static sun.misc.Unsafe getUnsafe() {
1101		try {
1102	<	if (ForkJoinWorkerThread.class.getClassLoader() != null) {
1103	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1104	<	f.setAccessible(true);
1105	<	_unsafe = (Unsafe)f.get(null);
1106	<	}
1107	<	else
1108	<	_unsafe = Unsafe.getUnsafe();
1109	<	baseOffset = _unsafe.objectFieldOffset
1110	<	(ForkJoinWorkerThread.class.getDeclaredField("base"));
1111	<	spOffset = _unsafe.objectFieldOffset
1112	<	(ForkJoinWorkerThread.class.getDeclaredField("sp"));
1113	<	runStateOffset = _unsafe.objectFieldOffset
1114	<	(ForkJoinWorkerThread.class.getDeclaredField("runState"));
1115	<	qBase = _unsafe.arrayBaseOffset(ForkJoinTask[].class);
1116	<	int s = _unsafe.arrayIndexScale(ForkJoinTask[].class);
1117	<	if ((s & (s-1)) != 0)
997	<	throw new Error("data type scale not a power of two");
998	<	qShift = 31 - Integer.numberOfLeadingZeros(s);
999	<	} catch (Exception e) {
1000	<	throw new RuntimeException("Could not initialize intrinsics", e);
1102	>	return sun.misc.Unsafe.getUnsafe();
1103	>	} catch (SecurityException se) {
1104	>	try {
1105	>	return java.security.AccessController.doPrivileged
1106	>	(new java.security
1107	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1108	>	public sun.misc.Unsafe run() throws Exception {
1109	>	java.lang.reflect.Field f = sun.misc
1110	>	.Unsafe.class.getDeclaredField("theUnsafe");
1111	>	f.setAccessible(true);
1112	>	return (sun.misc.Unsafe) f.get(null);
1113	>	}});
1114	>	} catch (java.security.PrivilegedActionException e) {
1115	>	throw new RuntimeException("Could not initialize intrinsics",
1116	>	e.getCause());
1117	>	}
1118		}
1119		}
1120		}

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