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*/ |
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package jsr166y; |
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import java.util.*; |
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|
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import java.util.concurrent.*; |
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import java.util.concurrent.atomic.*; |
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import java.util.concurrent.locks.*; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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|
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import java.util.Collection; |
12 |
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|
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/** |
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* A thread that is internally managed by a ForkJoinPool to execute |
15 |
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* ForkJoinTasks. This class additionally provides public |
16 |
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* <tt>static</tt> methods accessing some basic scheduling and |
17 |
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* execution mechanics for the <em>current</em> |
18 |
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* ForkJoinWorkerThread. These methods may be invoked only from within |
19 |
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* other ForkJoinTask computations. Attempts to invoke in other |
20 |
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* contexts result in exceptions or errors including |
23 |
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* ClassCastException. These methods enable construction of |
24 |
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* special-purpose task classes, as well as specialized idioms |
25 |
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* occasionally useful in ForkJoinTask processing. |
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> |
* A thread managed by a {@link ForkJoinPool}. This class is |
15 |
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* subclassable solely for the sake of adding functionality -- there |
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* are no overridable methods dealing with scheduling or |
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* execution. However, you can override initialization and termination |
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* methods surrounding the main task processing loop. If you do |
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* create such a subclass, you will also need to supply a custom |
20 |
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* ForkJoinWorkerThreadFactory to use it in a ForkJoinPool. |
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* |
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* <p>The form of supported static methods reflects the fact that |
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* worker threads may access and process tasks obtained in any of |
29 |
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* three ways. In preference order: <em>Local</em> tasks are processed |
30 |
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* in LIFO (newest first) order. <em>Stolen</em> tasks are obtained |
31 |
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* from other threads in FIFO (oldest first) order, only if there are |
32 |
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* no local tasks to run. <em>Submissions</em> form a FIFO queue |
33 |
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* common to the entire pool, and are started only if no other |
34 |
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* work is available. |
35 |
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* |
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* <p> This class is subclassable solely for the sake of adding |
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* functionality -- there are no overridable methods dealing with |
38 |
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* scheduling or execution. However, you can override initialization |
39 |
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* and termination cleanup methods surrounding the main task |
40 |
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* processing loop. If you do create such a subclass, you will also |
41 |
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* need to supply a custom ForkJoinWorkerThreadFactory to use it in a |
42 |
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* ForkJoinPool. |
22 |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
25 |
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public class ForkJoinWorkerThread extends Thread { |
26 |
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/* |
44 |
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* of tasks. To accomplish this, we shift the CAS arbitrating pop |
45 |
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* vs deq (steal) from being on the indices ("base" and "sp") to |
46 |
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* the slots themselves (mainly via method "casSlotNull()"). So, |
47 |
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* both a successful pop and deq mainly entail CAS'ing a nonnull |
47 |
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* both a successful pop and deq mainly entail CAS'ing a non-null |
48 |
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* slot to null. Because we rely on CASes of references, we do |
49 |
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* not need tag bits on base or sp. They are simple ints as used |
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* in any circular array-based queue (see for example ArrayDeque). |
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* considered individually, is not wait-free. One thief cannot |
57 |
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* successfully continue until another in-progress one (or, if |
58 |
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* previously empty, a push) completes. However, in the |
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* aggregate, we ensure at least probablistic non-blockingness. If |
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* aggregate, we ensure at least probabilistic non-blockingness. If |
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* an attempted steal fails, a thief always chooses a different |
61 |
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* random victim target to try next. So, in order for one thief to |
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* progress, it suffices for any in-progress deq or new push on |
75 |
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* push) require store order and CASes (in pop and deq) require |
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* (volatile) CAS semantics. Since these combinations aren't |
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* supported using ordinary volatiles, the only way to accomplish |
78 |
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* these effciently is to use direct Unsafe calls. (Using external |
78 |
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* these efficiently is to use direct Unsafe calls. (Using external |
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* AtomicIntegers and AtomicReferenceArrays for the indices and |
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* array is significantly slower because of memory locality and |
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* indirection effects.) Further, performance on most platforms is |
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|
131 |
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/** |
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* Maximum work-stealing queue array size. Must be less than or |
133 |
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* equal to 1 << 30 to ensure lack of index wraparound. |
133 |
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* equal to 1 << 28 to ensure lack of index wraparound. (This |
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* is less than usual bounds, because we need leftshift by 3 |
135 |
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* to be in int range). |
136 |
|
*/ |
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private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 30; |
137 |
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private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 28; |
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|
139 |
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/** |
140 |
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* Generator of seeds for per-thread random numbers. |
140 |
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* The pool this thread works in. Accessed directly by ForkJoinTask. |
141 |
|
*/ |
142 |
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private static final Random randomSeedGenerator = new Random(); |
142 |
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final ForkJoinPool pool; |
143 |
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|
144 |
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/** |
145 |
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* The work-stealing queue array. Size must be a power of two. |
146 |
+ |
* Initialized when thread starts, to improve memory locality. |
147 |
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*/ |
148 |
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private ForkJoinTask<?>[] queue; |
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|
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private volatile int base; |
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|
164 |
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/** |
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* The pool this thread works in. |
166 |
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*/ |
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final ForkJoinPool pool; |
168 |
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|
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/** |
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* Index of this worker in pool array. Set once by pool before |
187 |
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* running, and accessed directly by pool during cleanup etc |
165 |
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* Activity status. When true, this worker is considered active. |
166 |
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* Must be false upon construction. It must be true when executing |
167 |
> |
* tasks, and BEFORE stealing a task. It must be false before |
168 |
> |
* calling pool.sync. |
169 |
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*/ |
170 |
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int poolIndex; |
170 |
> |
private boolean active; |
171 |
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|
172 |
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/** |
173 |
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* Run state of this worker. Supports simple versions of the usual |
175 |
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*/ |
176 |
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private volatile int runState; |
177 |
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|
197 |
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// Runstate values. Order matters |
198 |
– |
private static final int RUNNING = 0; |
199 |
– |
private static final int SHUTDOWN = 1; |
200 |
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private static final int TERMINATING = 2; |
201 |
– |
private static final int TERMINATED = 3; |
202 |
– |
|
178 |
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/** |
179 |
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* Activity status. When true, this worker is considered active. |
180 |
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* Must be false upon construction. It must be true when executing |
206 |
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* tasks, and BEFORE stealing a task. It must be false before |
207 |
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* blocking on the Pool Barrier. |
179 |
> |
* Seed for random number generator for choosing steal victims. |
180 |
> |
* Uses Marsaglia xorshift. Must be nonzero upon initialization. |
181 |
|
*/ |
182 |
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private boolean active; |
182 |
> |
private int seed; |
183 |
|
|
184 |
|
/** |
185 |
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* Number of steals, transferred to pool when idle |
187 |
|
private int stealCount; |
188 |
|
|
189 |
|
/** |
190 |
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* Seed for random number generator for choosing steal victims |
190 |
> |
* Index of this worker in pool array. Set once by pool before |
191 |
> |
* running, and accessed directly by pool during cleanup etc. |
192 |
|
*/ |
193 |
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private int randomVictimSeed; |
193 |
> |
int poolIndex; |
194 |
|
|
195 |
|
/** |
196 |
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* Seed for embedded Jurandom |
196 |
> |
* The last barrier event waited for. Accessed in pool callback |
197 |
> |
* methods, but only by current thread. |
198 |
|
*/ |
199 |
< |
private long juRandomSeed; |
199 |
> |
long lastEventCount; |
200 |
|
|
201 |
|
/** |
202 |
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* The last barrier event waited for |
202 |
> |
* True if use local fifo, not default lifo, for local polling |
203 |
|
*/ |
204 |
< |
private long eventCount; |
204 |
> |
private boolean locallyFifo; |
205 |
|
|
206 |
|
/** |
207 |
|
* Creates a ForkJoinWorkerThread operating in the given pool. |
208 |
+ |
* |
209 |
|
* @param pool the pool this thread works in |
210 |
|
* @throws NullPointerException if pool is null |
211 |
|
*/ |
212 |
|
protected ForkJoinWorkerThread(ForkJoinPool pool) { |
213 |
|
if (pool == null) throw new NullPointerException(); |
214 |
|
this.pool = pool; |
215 |
< |
// remaining initialization deferred to onStart |
215 |
> |
// Note: poolIndex is set by pool during construction |
216 |
> |
// Remaining initialization is deferred to onStart |
217 |
|
} |
218 |
|
|
219 |
< |
// Access methods used by Pool |
219 |
> |
// Public access methods |
220 |
|
|
221 |
|
/** |
222 |
< |
* Get and clear steal count for accumulation by pool. Called |
223 |
< |
* only when known to be idle (in pool.sync and termination). |
222 |
> |
* Returns the pool hosting this thread. |
223 |
> |
* |
224 |
> |
* @return the pool |
225 |
|
*/ |
226 |
< |
final int getAndClearStealCount() { |
227 |
< |
int sc = stealCount; |
250 |
< |
stealCount = 0; |
251 |
< |
return sc; |
226 |
> |
public ForkJoinPool getPool() { |
227 |
> |
return pool; |
228 |
|
} |
229 |
|
|
230 |
|
/** |
231 |
< |
* Returns estimate of the number of tasks in the queue, without |
232 |
< |
* correcting for transient negative values |
231 |
> |
* Returns the index number of this thread in its pool. The |
232 |
> |
* returned value ranges from zero to the maximum number of |
233 |
> |
* threads (minus one) that have ever been created in the pool. |
234 |
> |
* This method may be useful for applications that track status or |
235 |
> |
* collect results per-worker rather than per-task. |
236 |
> |
* |
237 |
> |
* @return the index number |
238 |
|
*/ |
239 |
< |
final int getRawQueueSize() { |
240 |
< |
return sp - base; |
239 |
> |
public int getPoolIndex() { |
240 |
> |
return poolIndex; |
241 |
|
} |
242 |
|
|
243 |
< |
// Intrinsics-based support for queue operations. |
244 |
< |
// Currently these three (setSp, setSlot, casSlotNull) are |
245 |
< |
// usually manually inlined to improve performance |
243 |
> |
/** |
244 |
> |
* Establishes local first-in-first-out scheduling mode for forked |
245 |
> |
* tasks that are never joined. |
246 |
> |
* |
247 |
> |
* @param async if true, use locally FIFO scheduling |
248 |
> |
*/ |
249 |
> |
void setAsyncMode(boolean async) { |
250 |
> |
locallyFifo = async; |
251 |
> |
} |
252 |
> |
|
253 |
> |
// Runstate management |
254 |
> |
|
255 |
> |
// Runstate values. Order matters |
256 |
> |
private static final int RUNNING = 0; |
257 |
> |
private static final int SHUTDOWN = 1; |
258 |
> |
private static final int TERMINATING = 2; |
259 |
> |
private static final int TERMINATED = 3; |
260 |
> |
|
261 |
> |
final boolean isShutdown() { return runState >= SHUTDOWN; } |
262 |
> |
final boolean isTerminating() { return runState >= TERMINATING; } |
263 |
> |
final boolean isTerminated() { return runState == TERMINATED; } |
264 |
> |
final boolean shutdown() { return transitionRunStateTo(SHUTDOWN); } |
265 |
> |
final boolean shutdownNow() { return transitionRunStateTo(TERMINATING); } |
266 |
|
|
267 |
|
/** |
268 |
< |
* Sets sp in store-order. |
268 |
> |
* Transitions to at least the given state. Returns true if not |
269 |
> |
* already at least at given state. |
270 |
> |
*/ |
271 |
> |
private boolean transitionRunStateTo(int state) { |
272 |
> |
for (;;) { |
273 |
> |
int s = runState; |
274 |
> |
if (s >= state) |
275 |
> |
return false; |
276 |
> |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, state)) |
277 |
> |
return true; |
278 |
> |
} |
279 |
> |
} |
280 |
> |
|
281 |
> |
/** |
282 |
> |
* Tries to set status to active; fails on contention. |
283 |
> |
*/ |
284 |
> |
private boolean tryActivate() { |
285 |
> |
if (!active) { |
286 |
> |
if (!pool.tryIncrementActiveCount()) |
287 |
> |
return false; |
288 |
> |
active = true; |
289 |
> |
} |
290 |
> |
return true; |
291 |
> |
} |
292 |
> |
|
293 |
> |
/** |
294 |
> |
* Tries to set status to inactive; fails on contention. |
295 |
> |
*/ |
296 |
> |
private boolean tryInactivate() { |
297 |
> |
if (active) { |
298 |
> |
if (!pool.tryDecrementActiveCount()) |
299 |
> |
return false; |
300 |
> |
active = false; |
301 |
> |
} |
302 |
> |
return true; |
303 |
> |
} |
304 |
> |
|
305 |
> |
/** |
306 |
> |
* Computes next value for random victim probe. Scans don't |
307 |
> |
* require a very high quality generator, but also not a crummy |
308 |
> |
* one. Marsaglia xor-shift is cheap and works well. |
309 |
|
*/ |
310 |
< |
private void setSp(int s) { |
311 |
< |
_unsafe.putOrderedInt(this, spOffset, s); |
310 |
> |
private static int xorShift(int r) { |
311 |
> |
r ^= r << 1; |
312 |
> |
r ^= r >>> 3; |
313 |
> |
r ^= r << 10; |
314 |
> |
return r; |
315 |
|
} |
316 |
|
|
317 |
+ |
// Lifecycle methods |
318 |
+ |
|
319 |
|
/** |
320 |
< |
* Add in store-order the given task at given slot of q to |
321 |
< |
* null. Caller must ensure q is nonnull and index is in range. |
320 |
> |
* This method is required to be public, but should never be |
321 |
> |
* called explicitly. It performs the main run loop to execute |
322 |
> |
* ForkJoinTasks. |
323 |
> |
*/ |
324 |
> |
public void run() { |
325 |
> |
Throwable exception = null; |
326 |
> |
try { |
327 |
> |
onStart(); |
328 |
> |
pool.sync(this); // await first pool event |
329 |
> |
mainLoop(); |
330 |
> |
} catch (Throwable ex) { |
331 |
> |
exception = ex; |
332 |
> |
} finally { |
333 |
> |
onTermination(exception); |
334 |
> |
} |
335 |
> |
} |
336 |
> |
|
337 |
> |
/** |
338 |
> |
* Executes tasks until shut down. |
339 |
> |
*/ |
340 |
> |
private void mainLoop() { |
341 |
> |
while (!isShutdown()) { |
342 |
> |
ForkJoinTask<?> t = pollTask(); |
343 |
> |
if (t != null || (t = pollSubmission()) != null) |
344 |
> |
t.quietlyExec(); |
345 |
> |
else if (tryInactivate()) |
346 |
> |
pool.sync(this); |
347 |
> |
} |
348 |
> |
} |
349 |
> |
|
350 |
> |
/** |
351 |
> |
* Initializes internal state after construction but before |
352 |
> |
* processing any tasks. If you override this method, you must |
353 |
> |
* invoke super.onStart() at the beginning of the method. |
354 |
> |
* Initialization requires care: Most fields must have legal |
355 |
> |
* default values, to ensure that attempted accesses from other |
356 |
> |
* threads work correctly even before this thread starts |
357 |
> |
* processing tasks. |
358 |
> |
*/ |
359 |
> |
protected void onStart() { |
360 |
> |
// Allocate while starting to improve chances of thread-local |
361 |
> |
// isolation |
362 |
> |
queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
363 |
> |
// Initial value of seed need not be especially random but |
364 |
> |
// should differ across workers and must be nonzero |
365 |
> |
int p = poolIndex + 1; |
366 |
> |
seed = p + (p << 8) + (p << 16) + (p << 24); // spread bits |
367 |
> |
} |
368 |
> |
|
369 |
> |
/** |
370 |
> |
* Performs cleanup associated with termination of this worker |
371 |
> |
* thread. If you override this method, you must invoke |
372 |
> |
* {@code super.onTermination} at the end of the overridden method. |
373 |
> |
* |
374 |
> |
* @param exception the exception causing this thread to abort due |
375 |
> |
* to an unrecoverable error, or null if completed normally |
376 |
> |
*/ |
377 |
> |
protected void onTermination(Throwable exception) { |
378 |
> |
// Execute remaining local tasks unless aborting or terminating |
379 |
> |
while (exception == null && !pool.isTerminating() && base != sp) { |
380 |
> |
try { |
381 |
> |
ForkJoinTask<?> t = popTask(); |
382 |
> |
if (t != null) |
383 |
> |
t.quietlyExec(); |
384 |
> |
} catch (Throwable ex) { |
385 |
> |
exception = ex; |
386 |
> |
} |
387 |
> |
} |
388 |
> |
// Cancel other tasks, transition status, notify pool, and |
389 |
> |
// propagate exception to uncaught exception handler |
390 |
> |
try { |
391 |
> |
do {} while (!tryInactivate()); // ensure inactive |
392 |
> |
cancelTasks(); |
393 |
> |
runState = TERMINATED; |
394 |
> |
pool.workerTerminated(this); |
395 |
> |
} catch (Throwable ex) { // Shouldn't ever happen |
396 |
> |
if (exception == null) // but if so, at least rethrown |
397 |
> |
exception = ex; |
398 |
> |
} finally { |
399 |
> |
if (exception != null) |
400 |
> |
ForkJoinTask.rethrowException(exception); |
401 |
> |
} |
402 |
> |
} |
403 |
> |
|
404 |
> |
// Intrinsics-based support for queue operations. |
405 |
> |
|
406 |
> |
/** |
407 |
> |
* Adds in store-order the given task at given slot of q to null. |
408 |
> |
* Caller must ensure q is non-null and index is in range. |
409 |
|
*/ |
410 |
|
private static void setSlot(ForkJoinTask<?>[] q, int i, |
411 |
< |
ForkJoinTask<?> t){ |
412 |
< |
_unsafe.putOrderedObject(q, (i << qShift) + qBase, t); |
411 |
> |
ForkJoinTask<?> t) { |
412 |
> |
UNSAFE.putOrderedObject(q, (i << qShift) + qBase, t); |
413 |
|
} |
414 |
|
|
415 |
|
/** |
416 |
< |
* CAS given slot of q to null. Caller must ensure q is nonnull |
416 |
> |
* CAS given slot of q to null. Caller must ensure q is non-null |
417 |
|
* and index is in range. |
418 |
|
*/ |
419 |
|
private static boolean casSlotNull(ForkJoinTask<?>[] q, int i, |
420 |
|
ForkJoinTask<?> t) { |
421 |
< |
return _unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null); |
421 |
> |
return UNSAFE.compareAndSwapObject(q, (i << qShift) + qBase, t, null); |
422 |
> |
} |
423 |
> |
|
424 |
> |
/** |
425 |
> |
* Sets sp in store-order. |
426 |
> |
*/ |
427 |
> |
private void storeSp(int s) { |
428 |
> |
UNSAFE.putOrderedInt(this, spOffset, s); |
429 |
|
} |
430 |
|
|
431 |
|
// Main queue methods |
432 |
|
|
433 |
|
/** |
434 |
|
* Pushes a task. Called only by current thread. |
435 |
< |
* @param t the task. Caller must ensure nonnull |
435 |
> |
* |
436 |
> |
* @param t the task. Caller must ensure non-null. |
437 |
|
*/ |
438 |
|
final void pushTask(ForkJoinTask<?> t) { |
439 |
|
ForkJoinTask<?>[] q = queue; |
440 |
|
int mask = q.length - 1; |
441 |
|
int s = sp; |
442 |
< |
_unsafe.putOrderedObject(q, ((s & mask) << qShift) + qBase, t); |
443 |
< |
_unsafe.putOrderedInt(this, spOffset, ++s); |
442 |
> |
setSlot(q, s & mask, t); |
443 |
> |
storeSp(++s); |
444 |
|
if ((s -= base) == 1) |
445 |
< |
pool.signalNonEmptyWorkerQueue(); |
445 |
> |
pool.signalWork(); |
446 |
|
else if (s >= mask) |
447 |
|
growQueue(); |
448 |
|
} |
450 |
|
/** |
451 |
|
* Tries to take a task from the base of the queue, failing if |
452 |
|
* either empty or contended. |
453 |
< |
* @return a task, or null if none or contended. |
453 |
> |
* |
454 |
> |
* @return a task, or null if none or contended |
455 |
|
*/ |
456 |
< |
private ForkJoinTask<?> deqTask() { |
315 |
< |
ForkJoinTask<?>[] q; |
456 |
> |
final ForkJoinTask<?> deqTask() { |
457 |
|
ForkJoinTask<?> t; |
458 |
+ |
ForkJoinTask<?>[] q; |
459 |
|
int i; |
460 |
|
int b; |
461 |
|
if (sp != (b = base) && |
462 |
|
(q = queue) != null && // must read q after b |
463 |
|
(t = q[i = (q.length - 1) & b]) != null && |
464 |
< |
_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) { |
464 |
> |
casSlotNull(q, i, t)) { |
465 |
|
base = b + 1; |
466 |
|
return t; |
467 |
|
} |
469 |
|
} |
470 |
|
|
471 |
|
/** |
472 |
< |
* Returns a popped task, or null if empty. Called only by |
473 |
< |
* current thread. |
472 |
> |
* Returns a popped task, or null if empty. Ensures active status |
473 |
> |
* if non-null. Called only by current thread. |
474 |
|
*/ |
475 |
|
final ForkJoinTask<?> popTask() { |
334 |
– |
ForkJoinTask<?> t; |
335 |
– |
int i; |
336 |
– |
ForkJoinTask<?>[] q = queue; |
337 |
– |
int mask = q.length - 1; |
476 |
|
int s = sp; |
477 |
< |
if (s != base && |
478 |
< |
(t = q[i = (s - 1) & mask]) != null && |
479 |
< |
_unsafe.compareAndSwapObject(q, (i << qShift) + qBase, t, null)) { |
480 |
< |
_unsafe.putOrderedInt(this, spOffset, s - 1); |
481 |
< |
return t; |
477 |
> |
while (s != base) { |
478 |
> |
if (tryActivate()) { |
479 |
> |
ForkJoinTask<?>[] q = queue; |
480 |
> |
int mask = q.length - 1; |
481 |
> |
int i = (s - 1) & mask; |
482 |
> |
ForkJoinTask<?> t = q[i]; |
483 |
> |
if (t == null || !casSlotNull(q, i, t)) |
484 |
> |
break; |
485 |
> |
storeSp(s - 1); |
486 |
> |
return t; |
487 |
> |
} |
488 |
|
} |
489 |
|
return null; |
490 |
|
} |
492 |
|
/** |
493 |
|
* Specialized version of popTask to pop only if |
494 |
|
* topmost element is the given task. Called only |
495 |
< |
* by current thread. |
496 |
< |
* @param t the task. Caller must ensure nonnull |
495 |
> |
* by current thread while active. |
496 |
> |
* |
497 |
> |
* @param t the task. Caller must ensure non-null. |
498 |
|
*/ |
499 |
|
final boolean unpushTask(ForkJoinTask<?> t) { |
500 |
|
ForkJoinTask<?>[] q = queue; |
501 |
|
int mask = q.length - 1; |
502 |
|
int s = sp - 1; |
503 |
< |
if (_unsafe.compareAndSwapObject(q, ((s & mask) << qShift) + qBase, |
504 |
< |
t, null)) { |
360 |
< |
_unsafe.putOrderedInt(this, spOffset, s); |
503 |
> |
if (casSlotNull(q, s & mask, t)) { |
504 |
> |
storeSp(s); |
505 |
|
return true; |
506 |
|
} |
507 |
|
return false; |
508 |
|
} |
509 |
|
|
510 |
|
/** |
511 |
< |
* Returns next task to pop. |
511 |
> |
* Returns next task. |
512 |
|
*/ |
513 |
< |
private ForkJoinTask<?> peekTask() { |
513 |
> |
final ForkJoinTask<?> peekTask() { |
514 |
|
ForkJoinTask<?>[] q = queue; |
515 |
< |
return q == null? null : q[(sp - 1) & (q.length - 1)]; |
515 |
> |
if (q == null) |
516 |
> |
return null; |
517 |
> |
int mask = q.length - 1; |
518 |
> |
int i = locallyFifo ? base : (sp - 1); |
519 |
> |
return q[i & mask]; |
520 |
|
} |
521 |
|
|
522 |
|
/** |
543 |
|
t = null; |
544 |
|
setSlot(newQ, b & newMask, t); |
545 |
|
} while (++b != bf); |
546 |
< |
pool.signalIdleWorkers(false); |
399 |
< |
} |
400 |
< |
|
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 |
< |
|
409 |
< |
/** |
410 |
< |
* Transition to at least the given state. Return true if not |
411 |
< |
* already at least given state. |
412 |
< |
*/ |
413 |
< |
private boolean transitionRunStateTo(int state) { |
414 |
< |
for (;;) { |
415 |
< |
int s = runState; |
416 |
< |
if (s >= state) |
417 |
< |
return false; |
418 |
< |
if (_unsafe.compareAndSwapInt(this, runStateOffset, s, state)) |
419 |
< |
return true; |
420 |
< |
} |
546 |
> |
pool.signalWork(); |
547 |
|
} |
548 |
|
|
549 |
|
/** |
550 |
< |
* Ensure status is active and if necessary adjust pool active count |
551 |
< |
*/ |
552 |
< |
final void activate() { |
553 |
< |
if (!active) { |
554 |
< |
active = true; |
555 |
< |
pool.incrementActiveCount(); |
556 |
< |
} |
557 |
< |
} |
558 |
< |
|
559 |
< |
/** |
560 |
< |
* Ensure status is inactive and if necessary adjust pool active count |
550 |
> |
* Tries to steal a task from another worker. Starts at a random |
551 |
> |
* index of workers array, and probes workers until finding one |
552 |
> |
* with non-empty queue or finding that all are empty. It |
553 |
> |
* randomly selects the first n probes. If these are empty, it |
554 |
> |
* resorts to a full circular traversal, which is necessary to |
555 |
> |
* accurately set active status by caller. Also restarts if pool |
556 |
> |
* events occurred since last scan, which forces refresh of |
557 |
> |
* workers array, in case barrier was associated with resize. |
558 |
> |
* |
559 |
> |
* This method must be both fast and quiet -- usually avoiding |
560 |
> |
* memory accesses that could disrupt cache sharing etc other than |
561 |
> |
* those needed to check for and take tasks. This accounts for, |
562 |
> |
* among other things, updating random seed in place without |
563 |
> |
* storing it until exit. |
564 |
> |
* |
565 |
> |
* @return a task, or null if none found |
566 |
|
*/ |
567 |
< |
final void inactivate() { |
568 |
< |
if (active) { |
569 |
< |
active = false; |
570 |
< |
pool.decrementActiveCount(); |
571 |
< |
} |
567 |
> |
private ForkJoinTask<?> scan() { |
568 |
> |
ForkJoinTask<?> t = null; |
569 |
> |
int r = seed; // extract once to keep scan quiet |
570 |
> |
ForkJoinWorkerThread[] ws; // refreshed on outer loop |
571 |
> |
int mask; // must be power 2 minus 1 and > 0 |
572 |
> |
outer:do { |
573 |
> |
if ((ws = pool.workers) != null && (mask = ws.length - 1) > 0) { |
574 |
> |
int idx = r; |
575 |
> |
int probes = ~mask; // use random index while negative |
576 |
> |
for (;;) { |
577 |
> |
r = xorShift(r); // update random seed |
578 |
> |
ForkJoinWorkerThread v = ws[mask & idx]; |
579 |
> |
if (v == null || v.sp == v.base) { |
580 |
> |
if (probes <= mask) |
581 |
> |
idx = (probes++ < 0) ? r : (idx + 1); |
582 |
> |
else |
583 |
> |
break; |
584 |
> |
} |
585 |
> |
else if (!tryActivate() || (t = v.deqTask()) == null) |
586 |
> |
continue outer; // restart on contention |
587 |
> |
else |
588 |
> |
break outer; |
589 |
> |
} |
590 |
> |
} |
591 |
> |
} while (pool.hasNewSyncEvent(this)); // retry on pool events |
592 |
> |
seed = r; |
593 |
> |
return t; |
594 |
|
} |
595 |
|
|
443 |
– |
// Lifecycle methods |
444 |
– |
|
596 |
|
/** |
597 |
< |
* Initializes internal state after construction but before |
598 |
< |
* processing any tasks. If you override this method, you must |
599 |
< |
* 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. |
597 |
> |
* Gets and removes a local or stolen task. |
598 |
> |
* |
599 |
> |
* @return a task, if available |
600 |
|
*/ |
601 |
< |
protected void onStart() { |
602 |
< |
juRandomSeed = randomSeedGenerator.nextLong(); |
603 |
< |
do;while((randomVictimSeed = nextRandomInt()) == 0); // must be nonzero |
604 |
< |
if (queue == null) |
605 |
< |
queue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
459 |
< |
|
460 |
< |
// Heuristically allow one initial thread to warm up; others wait |
461 |
< |
if (poolIndex < pool.getParallelism() - 1) { |
462 |
< |
eventCount = pool.sync(this, 0); |
463 |
< |
activate(); |
464 |
< |
} |
601 |
> |
final ForkJoinTask<?> pollTask() { |
602 |
> |
ForkJoinTask<?> t = locallyFifo ? deqTask() : popTask(); |
603 |
> |
if (t == null && (t = scan()) != null) |
604 |
> |
++stealCount; |
605 |
> |
return t; |
606 |
|
} |
607 |
|
|
608 |
|
/** |
609 |
< |
* Perform cleanup associated with termination of this worker |
469 |
< |
* thread. If you override this method, you must invoke |
470 |
< |
* super.onTermination at the end of the overridden method. |
609 |
> |
* Gets a local task. |
610 |
|
* |
611 |
< |
* @param exception the exception causing this thread to abort due |
473 |
< |
* to an unrecoverable error, or null if completed normally. |
611 |
> |
* @return a task, if available |
612 |
|
*/ |
613 |
< |
protected void onTermination(Throwable exception) { |
614 |
< |
try { |
477 |
< |
clearLocalTasks(); |
478 |
< |
inactivate(); |
479 |
< |
cancelTasks(); |
480 |
< |
} finally { |
481 |
< |
terminate(exception); |
482 |
< |
} |
613 |
> |
final ForkJoinTask<?> pollLocalTask() { |
614 |
> |
return locallyFifo ? deqTask() : popTask(); |
615 |
|
} |
616 |
|
|
617 |
|
/** |
618 |
< |
* Notify pool of termination and, if exception is nonnull, |
619 |
< |
* rethrow it to trigger this thread's uncaughtExceptionHandler |
618 |
> |
* Returns a pool submission, if one exists, activating first. |
619 |
> |
* |
620 |
> |
* @return a submission, if available |
621 |
|
*/ |
622 |
< |
private void terminate(Throwable exception) { |
623 |
< |
transitionRunStateTo(TERMINATED); |
624 |
< |
try { |
625 |
< |
pool.workerTerminated(this); |
626 |
< |
} finally { |
627 |
< |
if (exception != null) |
495 |
< |
ForkJoinTask.rethrowException(exception); |
622 |
> |
private ForkJoinTask<?> pollSubmission() { |
623 |
> |
ForkJoinPool p = pool; |
624 |
> |
while (p.hasQueuedSubmissions()) { |
625 |
> |
ForkJoinTask<?> t; |
626 |
> |
if (tryActivate() && (t = p.pollSubmission()) != null) |
627 |
> |
return t; |
628 |
|
} |
629 |
+ |
return null; |
630 |
|
} |
631 |
|
|
632 |
< |
/** |
500 |
< |
* Run local tasks on exit from main. |
501 |
< |
*/ |
502 |
< |
private void clearLocalTasks() { |
503 |
< |
while (base != sp && !pool.isTerminating()) { |
504 |
< |
ForkJoinTask<?> t = popTask(); |
505 |
< |
if (t != null) { |
506 |
< |
activate(); // ensure active status |
507 |
< |
t.quietlyExec(); |
508 |
< |
} |
509 |
< |
} |
510 |
< |
} |
632 |
> |
// Methods accessed only by Pool |
633 |
|
|
634 |
|
/** |
635 |
|
* Removes and cancels all tasks in queue. Can be called from any |
636 |
|
* thread. |
637 |
|
*/ |
638 |
|
final void cancelTasks() { |
639 |
< |
while (base != sp) { |
640 |
< |
ForkJoinTask<?> t = deqTask(); |
641 |
< |
if (t != null) |
520 |
< |
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); |
539 |
< |
} |
639 |
> |
ForkJoinTask<?> t; |
640 |
> |
while (base != sp && (t = deqTask()) != null) |
641 |
> |
t.cancelIgnoringExceptions(); |
642 |
|
} |
643 |
|
|
644 |
|
/** |
645 |
< |
* Main top-level action. |
645 |
> |
* Drains tasks to given collection c. |
646 |
> |
* |
647 |
> |
* @return the number of tasks drained |
648 |
|
*/ |
649 |
< |
private void step() { |
650 |
< |
ForkJoinTask<?> t = sp != base? popTask() : null; |
651 |
< |
if (t != null || (t = scan(null, true)) != null) { |
652 |
< |
activate(); |
653 |
< |
t.quietlyExec(); |
654 |
< |
} |
551 |
< |
else { |
552 |
< |
inactivate(); |
553 |
< |
eventCount = pool.sync(this, eventCount); |
649 |
> |
final int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
650 |
> |
int n = 0; |
651 |
> |
ForkJoinTask<?> t; |
652 |
> |
while (base != sp && (t = deqTask()) != null) { |
653 |
> |
c.add(t); |
654 |
> |
++n; |
655 |
|
} |
656 |
+ |
return n; |
657 |
|
} |
658 |
|
|
557 |
– |
// scanning for and stealing tasks |
558 |
– |
|
659 |
|
/** |
660 |
< |
* Computes next value for random victim probe. Scans don't |
661 |
< |
* require a very high quality generator, but also not a crummy |
562 |
< |
* one. Marsaglia xor-shift is cheap and works well. |
563 |
< |
* |
564 |
< |
* This is currently unused, and manually inlined |
660 |
> |
* Gets and clears steal count for accumulation by pool. Called |
661 |
> |
* only when known to be idle (in pool.sync and termination). |
662 |
|
*/ |
663 |
< |
private static int xorShift(int r) { |
664 |
< |
r ^= r << 1; |
665 |
< |
r ^= r >>> 3; |
666 |
< |
r ^= r << 10; |
570 |
< |
return r; |
663 |
> |
final int getAndClearStealCount() { |
664 |
> |
int sc = stealCount; |
665 |
> |
stealCount = 0; |
666 |
> |
return sc; |
667 |
|
} |
668 |
|
|
669 |
|
/** |
670 |
< |
* Tries to steal a task from another worker and/or, if enabled, |
671 |
< |
* submission queue. Starts at a random index of workers array, |
576 |
< |
* and probes workers until finding one with non-empty queue or |
577 |
< |
* finding that all are empty. It randomly selects the first n-1 |
578 |
< |
* probes. If these are empty, it resorts to full circular |
579 |
< |
* traversal, which is necessary to accurately set active status |
580 |
< |
* by caller. Also restarts if pool barrier has tripped since last |
581 |
< |
* scan, which forces refresh of workers array, in case barrier |
582 |
< |
* was associated with resize. |
583 |
< |
* |
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.) |
670 |
> |
* Returns true if at least one worker in the given array appears |
671 |
> |
* to have at least one queued task. |
672 |
|
* |
673 |
< |
* @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 |
673 |
> |
* @param ws array of workers |
674 |
|
*/ |
675 |
< |
private ForkJoinTask<?> scan(ForkJoinTask<?> joinMe, |
676 |
< |
boolean checkSubmissions) { |
677 |
< |
ForkJoinPool p = pool; |
678 |
< |
if (p == null) // Never null, but avoids |
679 |
< |
return null; // implicit nullchecks below |
680 |
< |
int r = randomVictimSeed; // extract once to keep scan quiet |
681 |
< |
restart: // outer loop refreshes ws array |
682 |
< |
while (joinMe == null || joinMe.status >= 0) { |
604 |
< |
int mask; |
605 |
< |
ForkJoinWorkerThread[] ws = p.workers; |
606 |
< |
if (ws != null && (mask = ws.length - 1) > 0) { |
607 |
< |
int probes = -mask; // use random index while negative |
608 |
< |
int idx = r; |
609 |
< |
for (;;) { |
610 |
< |
ForkJoinWorkerThread v; |
611 |
< |
// inlined xorshift to update seed |
612 |
< |
r ^= r << 1; r ^= r >>> 3; r ^= r << 10; |
613 |
< |
if ((v = ws[mask & idx]) != null && v.sp != v.base) { |
614 |
< |
ForkJoinTask<?> t; |
615 |
< |
activate(); |
616 |
< |
if ((joinMe == null || joinMe.status >= 0) && |
617 |
< |
(t = v.deqTask()) != null) { |
618 |
< |
randomVictimSeed = r; |
619 |
< |
++stealCount; |
620 |
< |
return t; |
621 |
< |
} |
622 |
< |
continue restart; // restart on contention |
623 |
< |
} |
624 |
< |
if ((probes >> 1) <= mask) // n-1 random then circular |
625 |
< |
idx = (probes++ < 0)? r : (idx + 1); |
626 |
< |
else |
627 |
< |
break; |
675 |
> |
static boolean hasQueuedTasks(ForkJoinWorkerThread[] ws) { |
676 |
> |
if (ws != null) { |
677 |
> |
int len = ws.length; |
678 |
> |
for (int j = 0; j < 2; ++j) { // need two passes for clean sweep |
679 |
> |
for (int i = 0; i < len; ++i) { |
680 |
> |
ForkJoinWorkerThread w = ws[i]; |
681 |
> |
if (w != null && w.sp != w.base) |
682 |
> |
return true; |
683 |
|
} |
684 |
|
} |
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; |
685 |
|
} |
686 |
+ |
return false; |
687 |
|
} |
688 |
|
|
689 |
< |
/** |
663 |
< |
* Implements ForkJoinTask.helpJoin |
664 |
< |
*/ |
665 |
< |
final int helpJoinTask(ForkJoinTask<?> joinMe) { |
666 |
< |
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 |
< |
} |
678 |
< |
} |
679 |
< |
if (t != null) // unsteal |
680 |
< |
pushTask(t); |
681 |
< |
return s; |
682 |
< |
} |
683 |
< |
|
684 |
< |
// Support for public static and/or ForkJoinTask methods |
689 |
> |
// Support methods for ForkJoinTask |
690 |
|
|
691 |
|
/** |
692 |
|
* Returns an estimate of the number of tasks in the queue. |
693 |
|
*/ |
694 |
|
final int getQueueSize() { |
695 |
< |
int b = base; |
696 |
< |
int n = sp - b; |
692 |
< |
return n <= 0? 0 : n; // suppress momentarily negative values |
693 |
< |
} |
694 |
< |
|
695 |
< |
/** |
696 |
< |
* Runs one popped task, if available |
697 |
< |
* @return true if ran a task |
698 |
< |
*/ |
699 |
< |
private boolean runLocalTask() { |
700 |
< |
ForkJoinTask<?> t = popTask(); |
701 |
< |
if (t == null) |
702 |
< |
return false; |
703 |
< |
t.quietlyExec(); |
704 |
< |
return true; |
705 |
< |
} |
706 |
< |
|
707 |
< |
/** |
708 |
< |
* Pops or steals a task |
709 |
< |
* @return task, or null if none available |
710 |
< |
*/ |
711 |
< |
private ForkJoinTask<?> getLocalOrStolenTask() { |
712 |
< |
ForkJoinTask<?> t = popTask(); |
713 |
< |
return t != null? t : scan(null, false); |
714 |
< |
} |
715 |
< |
|
716 |
< |
/** |
717 |
< |
* Runs a popped or stolen task, if available |
718 |
< |
* @return true if ran a task |
719 |
< |
*/ |
720 |
< |
private boolean runLocalOrStolenTask() { |
721 |
< |
ForkJoinTask<?> t = getLocalOrStolenTask(); |
722 |
< |
if (t == null) |
723 |
< |
return false; |
724 |
< |
t.quietlyExec(); |
725 |
< |
return true; |
726 |
< |
} |
727 |
< |
|
728 |
< |
/** |
729 |
< |
* Runs tasks until pool isQuiescent |
730 |
< |
*/ |
731 |
< |
final void helpQuiescePool() { |
732 |
< |
activate(); |
733 |
< |
for (;;) { |
734 |
< |
if (!runLocalOrStolenTask()) { |
735 |
< |
inactivate(); |
736 |
< |
if (pool.isQuiescent()) { |
737 |
< |
activate(); // re-activate on exit |
738 |
< |
break; |
739 |
< |
} |
740 |
< |
} |
741 |
< |
} |
695 |
> |
// suppress momentarily negative values |
696 |
> |
return Math.max(0, sp - base); |
697 |
|
} |
698 |
|
|
699 |
|
/** |
701 |
|
* function of number of idle workers. |
702 |
|
*/ |
703 |
|
final int getEstimatedSurplusTaskCount() { |
704 |
+ |
// The halving approximates weighting idle vs non-idle workers |
705 |
|
return (sp - base) - (pool.getIdleThreadCount() >>> 1); |
706 |
|
} |
707 |
|
|
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 |
– |
} |
785 |
– |
|
786 |
– |
/** |
787 |
– |
* Returns, but does not remove or execute, the next task locally |
788 |
– |
* queued for execution by the current worker thread. There is no |
789 |
– |
* guarantee that this task will be the next one actually returned |
790 |
– |
* or executed from other polling or execution methods. |
791 |
– |
* @return the next task or null if none |
792 |
– |
*/ |
793 |
– |
public static ForkJoinTask<?> peekLocalTask() { |
794 |
– |
return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask(); |
795 |
– |
} |
796 |
– |
|
708 |
|
/** |
709 |
< |
* 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 |
709 |
> |
* Scans, returning early if joinMe done. |
710 |
|
*/ |
711 |
< |
public static ForkJoinTask<?> pollLocalTask() { |
712 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask(); |
713 |
< |
} |
714 |
< |
|
715 |
< |
/** |
716 |
< |
* Execute the next task locally queued by the current worker, if |
717 |
< |
* 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 |
< |
} |
816 |
< |
|
817 |
< |
/** |
818 |
< |
* Removes and returns, without executing, the next task queued |
819 |
< |
* for execution in the current worker thread's local queue or if |
820 |
< |
* none, a task stolen from another worker, if one is available. |
821 |
< |
* 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(); |
711 |
> |
final ForkJoinTask<?> scanWhileJoining(ForkJoinTask<?> joinMe) { |
712 |
> |
ForkJoinTask<?> t = pollTask(); |
713 |
> |
if (t != null && joinMe.status < 0 && sp == base) { |
714 |
> |
pushTask(t); // unsteal if done and this task would be stealable |
715 |
> |
t = null; |
716 |
> |
} |
717 |
> |
return t; |
718 |
|
} |
719 |
|
|
720 |
|
/** |
721 |
< |
* 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() && !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. |
721 |
> |
* Runs tasks until {@code pool.isQuiescent()}. |
722 |
|
*/ |
723 |
< |
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 |
< |
|
723 |
> |
final void helpQuiescePool() { |
724 |
|
for (;;) { |
725 |
< |
int val = bits % n; |
726 |
< |
if (bits - val + (n-1) >= 0) |
727 |
< |
return val; |
728 |
< |
bits = nextJURandom(31); |
725 |
> |
ForkJoinTask<?> t = pollTask(); |
726 |
> |
if (t != null) |
727 |
> |
t.quietlyExec(); |
728 |
> |
else if (tryInactivate() && pool.isQuiescent()) |
729 |
> |
break; |
730 |
|
} |
731 |
+ |
do {} while (!tryActivate()); // re-activate on exit |
732 |
|
} |
733 |
|
|
734 |
< |
private final long nextJURandomLong() { |
735 |
< |
return ((long)(nextJURandom(32)) << 32) + nextJURandom(32); |
736 |
< |
} |
737 |
< |
|
738 |
< |
private final long nextJURandomLong(long n) { |
739 |
< |
if (n <= 0) |
740 |
< |
throw new IllegalArgumentException("n must be positive"); |
741 |
< |
long offset = 0; |
742 |
< |
while (n >= Integer.MAX_VALUE) { // randomly pick half range |
743 |
< |
int bits = nextJURandom(2); // 2nd bit for odd vs even split |
744 |
< |
long half = n >>> 1; |
745 |
< |
long nextn = ((bits & 2) == 0)? half : n - half; |
746 |
< |
if ((bits & 1) == 0) |
747 |
< |
offset += n - nextn; |
748 |
< |
n = nextn; |
734 |
> |
// Unsafe mechanics for jsr166y 3rd party package. |
735 |
> |
private static sun.misc.Unsafe getUnsafe() { |
736 |
> |
try { |
737 |
> |
return sun.misc.Unsafe.getUnsafe(); |
738 |
> |
} catch (SecurityException se) { |
739 |
> |
try { |
740 |
> |
return java.security.AccessController.doPrivileged |
741 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
742 |
> |
public sun.misc.Unsafe run() throws Exception { |
743 |
> |
return getUnsafeByReflection(); |
744 |
> |
}}); |
745 |
> |
} catch (java.security.PrivilegedActionException e) { |
746 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
747 |
> |
e.getCause()); |
748 |
> |
} |
749 |
|
} |
894 |
– |
return offset + nextJURandomInt((int)n); |
750 |
|
} |
751 |
|
|
752 |
< |
private final double nextJURandomDouble() { |
753 |
< |
return (((long)(nextJURandom(26)) << 27) + nextJURandom(27)) |
754 |
< |
/ (double)(1L << 53); |
752 |
> |
private static sun.misc.Unsafe getUnsafeByReflection() |
753 |
> |
throws NoSuchFieldException, IllegalAccessException { |
754 |
> |
java.lang.reflect.Field f = |
755 |
> |
sun.misc.Unsafe.class.getDeclaredField("theUnsafe"); |
756 |
> |
f.setAccessible(true); |
757 |
> |
return (sun.misc.Unsafe) f.get(null); |
758 |
|
} |
759 |
|
|
760 |
< |
/** |
761 |
< |
* Returns a random integer using a per-worker random |
762 |
< |
* number generator with the same properties as |
763 |
< |
* {@link java.util.Random#nextInt} |
764 |
< |
* @return the next pseudorandom, uniformly distributed {@code int} |
765 |
< |
* value from this worker's random number generator's sequence |
766 |
< |
*/ |
767 |
< |
public static int nextRandomInt() { |
768 |
< |
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 |
965 |
< |
*/ |
966 |
< |
public static double nextRandomDouble() { |
967 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
968 |
< |
nextJURandomDouble(); |
760 |
> |
private static long fieldOffset(String fieldName, Class<?> klazz) { |
761 |
> |
try { |
762 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName)); |
763 |
> |
} catch (NoSuchFieldException e) { |
764 |
> |
// Convert Exception to Error |
765 |
> |
NoSuchFieldError error = new NoSuchFieldError(fieldName); |
766 |
> |
error.initCause(e); |
767 |
> |
throw error; |
768 |
> |
} |
769 |
|
} |
770 |
|
|
771 |
< |
// Temporary Unsafe mechanics for preliminary release |
772 |
< |
|
773 |
< |
static final Unsafe _unsafe; |
774 |
< |
static final long baseOffset; |
775 |
< |
static final long spOffset; |
771 |
> |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
772 |
> |
static final long baseOffset = |
773 |
> |
fieldOffset("base", ForkJoinWorkerThread.class); |
774 |
> |
static final long spOffset = |
775 |
> |
fieldOffset("sp", ForkJoinWorkerThread.class); |
776 |
> |
static final long runStateOffset = |
777 |
> |
fieldOffset("runState", ForkJoinWorkerThread.class); |
778 |
|
static final long qBase; |
779 |
|
static final int qShift; |
780 |
< |
static final long runStateOffset; |
780 |
> |
|
781 |
|
static { |
782 |
< |
try { |
783 |
< |
if (ForkJoinWorkerThread.class.getClassLoader() != null) { |
784 |
< |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
785 |
< |
f.setAccessible(true); |
786 |
< |
_unsafe = (Unsafe)f.get(null); |
985 |
< |
} |
986 |
< |
else |
987 |
< |
_unsafe = Unsafe.getUnsafe(); |
988 |
< |
baseOffset = _unsafe.objectFieldOffset |
989 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("base")); |
990 |
< |
spOffset = _unsafe.objectFieldOffset |
991 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("sp")); |
992 |
< |
runStateOffset = _unsafe.objectFieldOffset |
993 |
< |
(ForkJoinWorkerThread.class.getDeclaredField("runState")); |
994 |
< |
qBase = _unsafe.arrayBaseOffset(ForkJoinTask[].class); |
995 |
< |
int s = _unsafe.arrayIndexScale(ForkJoinTask[].class); |
996 |
< |
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); |
1001 |
< |
} |
782 |
> |
qBase = UNSAFE.arrayBaseOffset(ForkJoinTask[].class); |
783 |
> |
int s = UNSAFE.arrayIndexScale(ForkJoinTask[].class); |
784 |
> |
if ((s & (s-1)) != 0) |
785 |
> |
throw new Error("data type scale not a power of two"); |
786 |
> |
qShift = 31 - Integer.numberOfLeadingZeros(s); |
787 |
|
} |
788 |
|
} |