1 |
dl |
1.1 |
/* |
2 |
|
|
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
|
|
* Expert Group and released to the public domain, as explained at |
4 |
jsr166 |
1.97 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
dl |
1.1 |
*/ |
6 |
|
|
|
7 |
|
|
package jsr166y; |
8 |
jsr166 |
1.22 |
|
9 |
|
|
import java.util.ArrayList; |
10 |
|
|
import java.util.Arrays; |
11 |
|
|
import java.util.Collection; |
12 |
|
|
import java.util.Collections; |
13 |
|
|
import java.util.List; |
14 |
dl |
1.91 |
import java.util.Random; |
15 |
dl |
1.78 |
import java.util.concurrent.AbstractExecutorService; |
16 |
|
|
import java.util.concurrent.Callable; |
17 |
|
|
import java.util.concurrent.ExecutorService; |
18 |
|
|
import java.util.concurrent.Future; |
19 |
|
|
import java.util.concurrent.RejectedExecutionException; |
20 |
|
|
import java.util.concurrent.RunnableFuture; |
21 |
|
|
import java.util.concurrent.TimeUnit; |
22 |
|
|
import java.util.concurrent.atomic.AtomicInteger; |
23 |
jsr166 |
1.22 |
import java.util.concurrent.locks.LockSupport; |
24 |
|
|
import java.util.concurrent.locks.ReentrantLock; |
25 |
dl |
1.91 |
import java.util.concurrent.locks.Condition; |
26 |
dl |
1.1 |
|
27 |
|
|
/** |
28 |
jsr166 |
1.29 |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
29 |
jsr166 |
1.39 |
* A {@code ForkJoinPool} provides the entry point for submissions |
30 |
dl |
1.57 |
* from non-{@code ForkJoinTask} clients, as well as management and |
31 |
jsr166 |
1.48 |
* monitoring operations. |
32 |
dl |
1.1 |
* |
33 |
dl |
1.42 |
* <p>A {@code ForkJoinPool} differs from other kinds of {@link |
34 |
|
|
* ExecutorService} mainly by virtue of employing |
35 |
|
|
* <em>work-stealing</em>: all threads in the pool attempt to find and |
36 |
|
|
* execute subtasks created by other active tasks (eventually blocking |
37 |
|
|
* waiting for work if none exist). This enables efficient processing |
38 |
|
|
* when most tasks spawn other subtasks (as do most {@code |
39 |
dl |
1.57 |
* ForkJoinTask}s). When setting <em>asyncMode</em> to true in |
40 |
|
|
* constructors, {@code ForkJoinPool}s may also be appropriate for use |
41 |
|
|
* with event-style tasks that are never joined. |
42 |
dl |
1.1 |
* |
43 |
dl |
1.42 |
* <p>A {@code ForkJoinPool} is constructed with a given target |
44 |
|
|
* parallelism level; by default, equal to the number of available |
45 |
dl |
1.57 |
* processors. The pool attempts to maintain enough active (or |
46 |
|
|
* available) threads by dynamically adding, suspending, or resuming |
47 |
|
|
* internal worker threads, even if some tasks are stalled waiting to |
48 |
|
|
* join others. However, no such adjustments are guaranteed in the |
49 |
|
|
* face of blocked IO or other unmanaged synchronization. The nested |
50 |
|
|
* {@link ManagedBlocker} interface enables extension of the kinds of |
51 |
|
|
* synchronization accommodated. |
52 |
dl |
1.1 |
* |
53 |
|
|
* <p>In addition to execution and lifecycle control methods, this |
54 |
|
|
* class provides status check methods (for example |
55 |
jsr166 |
1.29 |
* {@link #getStealCount}) that are intended to aid in developing, |
56 |
dl |
1.1 |
* tuning, and monitoring fork/join applications. Also, method |
57 |
jsr166 |
1.29 |
* {@link #toString} returns indications of pool state in a |
58 |
dl |
1.2 |
* convenient form for informal monitoring. |
59 |
dl |
1.1 |
* |
60 |
dl |
1.57 |
* <p> As is the case with other ExecutorServices, there are three |
61 |
dl |
1.60 |
* main task execution methods summarized in the following |
62 |
dl |
1.57 |
* table. These are designed to be used by clients not already engaged |
63 |
|
|
* in fork/join computations in the current pool. The main forms of |
64 |
|
|
* these methods accept instances of {@code ForkJoinTask}, but |
65 |
|
|
* overloaded forms also allow mixed execution of plain {@code |
66 |
|
|
* Runnable}- or {@code Callable}- based activities as well. However, |
67 |
|
|
* tasks that are already executing in a pool should normally |
68 |
|
|
* <em>NOT</em> use these pool execution methods, but instead use the |
69 |
dl |
1.59 |
* within-computation forms listed in the table. |
70 |
dl |
1.57 |
* |
71 |
|
|
* <table BORDER CELLPADDING=3 CELLSPACING=1> |
72 |
|
|
* <tr> |
73 |
|
|
* <td></td> |
74 |
|
|
* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td> |
75 |
|
|
* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td> |
76 |
|
|
* </tr> |
77 |
|
|
* <tr> |
78 |
jsr166 |
1.67 |
* <td> <b>Arrange async execution</td> |
79 |
dl |
1.57 |
* <td> {@link #execute(ForkJoinTask)}</td> |
80 |
|
|
* <td> {@link ForkJoinTask#fork}</td> |
81 |
|
|
* </tr> |
82 |
|
|
* <tr> |
83 |
|
|
* <td> <b>Await and obtain result</td> |
84 |
|
|
* <td> {@link #invoke(ForkJoinTask)}</td> |
85 |
|
|
* <td> {@link ForkJoinTask#invoke}</td> |
86 |
|
|
* </tr> |
87 |
|
|
* <tr> |
88 |
|
|
* <td> <b>Arrange exec and obtain Future</td> |
89 |
|
|
* <td> {@link #submit(ForkJoinTask)}</td> |
90 |
|
|
* <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td> |
91 |
|
|
* </tr> |
92 |
|
|
* </table> |
93 |
dl |
1.59 |
* |
94 |
dl |
1.42 |
* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is |
95 |
|
|
* used for all parallel task execution in a program or subsystem. |
96 |
|
|
* Otherwise, use would not usually outweigh the construction and |
97 |
|
|
* bookkeeping overhead of creating a large set of threads. For |
98 |
jsr166 |
1.43 |
* example, a common pool could be used for the {@code SortTasks} |
99 |
dl |
1.42 |
* illustrated in {@link RecursiveAction}. Because {@code |
100 |
|
|
* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon |
101 |
jsr166 |
1.43 |
* daemon} mode, there is typically no need to explicitly {@link |
102 |
dl |
1.42 |
* #shutdown} such a pool upon program exit. |
103 |
|
|
* |
104 |
jsr166 |
1.105 |
* <pre> {@code |
105 |
dl |
1.42 |
* static final ForkJoinPool mainPool = new ForkJoinPool(); |
106 |
|
|
* ... |
107 |
|
|
* public void sort(long[] array) { |
108 |
|
|
* mainPool.invoke(new SortTask(array, 0, array.length)); |
109 |
jsr166 |
1.105 |
* }}</pre> |
110 |
dl |
1.42 |
* |
111 |
dl |
1.1 |
* <p><b>Implementation notes</b>: This implementation restricts the |
112 |
dl |
1.2 |
* maximum number of running threads to 32767. Attempts to create |
113 |
jsr166 |
1.48 |
* pools with greater than the maximum number result in |
114 |
jsr166 |
1.39 |
* {@code IllegalArgumentException}. |
115 |
jsr166 |
1.16 |
* |
116 |
jsr166 |
1.48 |
* <p>This implementation rejects submitted tasks (that is, by throwing |
117 |
dl |
1.58 |
* {@link RejectedExecutionException}) only when the pool is shut down |
118 |
dl |
1.62 |
* or internal resources have been exhausted. |
119 |
jsr166 |
1.48 |
* |
120 |
jsr166 |
1.16 |
* @since 1.7 |
121 |
|
|
* @author Doug Lea |
122 |
dl |
1.1 |
*/ |
123 |
dl |
1.2 |
public class ForkJoinPool extends AbstractExecutorService { |
124 |
dl |
1.1 |
|
125 |
|
|
/* |
126 |
dl |
1.53 |
* Implementation Overview |
127 |
|
|
* |
128 |
|
|
* This class provides the central bookkeeping and control for a |
129 |
|
|
* set of worker threads: Submissions from non-FJ threads enter |
130 |
|
|
* into a submission queue. Workers take these tasks and typically |
131 |
|
|
* split them into subtasks that may be stolen by other workers. |
132 |
dl |
1.91 |
* Preference rules give first priority to processing tasks from |
133 |
|
|
* their own queues (LIFO or FIFO, depending on mode), then to |
134 |
|
|
* randomized FIFO steals of tasks in other worker queues, and |
135 |
|
|
* lastly to new submissions. |
136 |
|
|
* |
137 |
|
|
* The main throughput advantages of work-stealing stem from |
138 |
|
|
* decentralized control -- workers mostly take tasks from |
139 |
|
|
* themselves or each other. We cannot negate this in the |
140 |
|
|
* implementation of other management responsibilities. The main |
141 |
|
|
* tactic for avoiding bottlenecks is packing nearly all |
142 |
|
|
* essentially atomic control state into a single 64bit volatile |
143 |
|
|
* variable ("ctl"). This variable is read on the order of 10-100 |
144 |
|
|
* times as often as it is modified (always via CAS). (There is |
145 |
|
|
* some additional control state, for example variable "shutdown" |
146 |
|
|
* for which we can cope with uncoordinated updates.) This |
147 |
|
|
* streamlines synchronization and control at the expense of messy |
148 |
|
|
* constructions needed to repack status bits upon updates. |
149 |
|
|
* Updates tend not to contend with each other except during |
150 |
|
|
* bursts while submitted tasks begin or end. In some cases when |
151 |
|
|
* they do contend, threads can instead do something else |
152 |
dl |
1.95 |
* (usually, scan for tasks) until contention subsides. |
153 |
dl |
1.91 |
* |
154 |
|
|
* To enable packing, we restrict maximum parallelism to (1<<15)-1 |
155 |
|
|
* (which is far in excess of normal operating range) to allow |
156 |
|
|
* ids, counts, and their negations (used for thresholding) to fit |
157 |
|
|
* into 16bit fields. |
158 |
|
|
* |
159 |
|
|
* Recording Workers. Workers are recorded in the "workers" array |
160 |
|
|
* that is created upon pool construction and expanded if (rarely) |
161 |
|
|
* necessary. This is an array as opposed to some other data |
162 |
|
|
* structure to support index-based random steals by workers. |
163 |
|
|
* Updates to the array recording new workers and unrecording |
164 |
|
|
* terminated ones are protected from each other by a seqLock |
165 |
|
|
* (scanGuard) but the array is otherwise concurrently readable, |
166 |
|
|
* and accessed directly by workers. To simplify index-based |
167 |
|
|
* operations, the array size is always a power of two, and all |
168 |
|
|
* readers must tolerate null slots. To avoid flailing during |
169 |
|
|
* start-up, the array is presized to hold twice #parallelism |
170 |
|
|
* workers (which is unlikely to need further resizing during |
171 |
|
|
* execution). But to avoid dealing with so many null slots, |
172 |
|
|
* variable scanGuard includes a mask for the nearest power of two |
173 |
|
|
* that contains all current workers. All worker thread creation |
174 |
|
|
* is on-demand, triggered by task submissions, replacement of |
175 |
|
|
* terminated workers, and/or compensation for blocked |
176 |
|
|
* workers. However, all other support code is set up to work with |
177 |
|
|
* other policies. To ensure that we do not hold on to worker |
178 |
|
|
* references that would prevent GC, ALL accesses to workers are |
179 |
|
|
* via indices into the workers array (which is one source of some |
180 |
|
|
* of the messy code constructions here). In essence, the workers |
181 |
|
|
* array serves as a weak reference mechanism. Thus for example |
182 |
|
|
* the wait queue field of ctl stores worker indices, not worker |
183 |
|
|
* references. Access to the workers in associated methods (for |
184 |
|
|
* example signalWork) must both index-check and null-check the |
185 |
|
|
* IDs. All such accesses ignore bad IDs by returning out early |
186 |
|
|
* from what they are doing, since this can only be associated |
187 |
|
|
* with termination, in which case it is OK to give up. |
188 |
|
|
* |
189 |
|
|
* All uses of the workers array, as well as queue arrays, check |
190 |
|
|
* that the array is non-null (even if previously non-null). This |
191 |
|
|
* allows nulling during termination, which is currently not |
192 |
|
|
* necessary, but remains an option for resource-revocation-based |
193 |
|
|
* shutdown schemes. |
194 |
|
|
* |
195 |
|
|
* Wait Queuing. Unlike HPC work-stealing frameworks, we cannot |
196 |
dl |
1.95 |
* let workers spin indefinitely scanning for tasks when none can |
197 |
|
|
* be found immediately, and we cannot start/resume workers unless |
198 |
|
|
* there appear to be tasks available. On the other hand, we must |
199 |
|
|
* quickly prod them into action when new tasks are submitted or |
200 |
|
|
* generated. We park/unpark workers after placing in an event |
201 |
|
|
* wait queue when they cannot find work. This "queue" is actually |
202 |
|
|
* a simple Treiber stack, headed by the "id" field of ctl, plus a |
203 |
|
|
* 15bit counter value to both wake up waiters (by advancing their |
204 |
|
|
* count) and avoid ABA effects. Successors are held in worker |
205 |
|
|
* field "nextWait". Queuing deals with several intrinsic races, |
206 |
|
|
* mainly that a task-producing thread can miss seeing (and |
207 |
|
|
* signalling) another thread that gave up looking for work but |
208 |
|
|
* has not yet entered the wait queue. We solve this by requiring |
209 |
|
|
* a full sweep of all workers both before (in scan()) and after |
210 |
|
|
* (in tryAwaitWork()) a newly waiting worker is added to the wait |
211 |
|
|
* queue. During a rescan, the worker might release some other |
212 |
|
|
* queued worker rather than itself, which has the same net |
213 |
|
|
* effect. Because enqueued workers may actually be rescanning |
214 |
|
|
* rather than waiting, we set and clear the "parked" field of |
215 |
|
|
* ForkJoinWorkerThread to reduce unnecessary calls to unpark. |
216 |
|
|
* (Use of the parked field requires a secondary recheck to avoid |
217 |
|
|
* missed signals.) |
218 |
dl |
1.91 |
* |
219 |
|
|
* Signalling. We create or wake up workers only when there |
220 |
|
|
* appears to be at least one task they might be able to find and |
221 |
|
|
* execute. When a submission is added or another worker adds a |
222 |
|
|
* task to a queue that previously had two or fewer tasks, they |
223 |
|
|
* signal waiting workers (or trigger creation of new ones if |
224 |
|
|
* fewer than the given parallelism level -- see signalWork). |
225 |
|
|
* These primary signals are buttressed by signals during rescans |
226 |
|
|
* as well as those performed when a worker steals a task and |
227 |
|
|
* notices that there are more tasks too; together these cover the |
228 |
|
|
* signals needed in cases when more than two tasks are pushed |
229 |
|
|
* but untaken. |
230 |
|
|
* |
231 |
|
|
* Trimming workers. To release resources after periods of lack of |
232 |
|
|
* use, a worker starting to wait when the pool is quiescent will |
233 |
|
|
* time out and terminate if the pool has remained quiescent for |
234 |
dl |
1.95 |
* SHRINK_RATE nanosecs. This will slowly propagate, eventually |
235 |
|
|
* terminating all workers after long periods of non-use. |
236 |
dl |
1.91 |
* |
237 |
|
|
* Submissions. External submissions are maintained in an |
238 |
|
|
* array-based queue that is structured identically to |
239 |
dl |
1.95 |
* ForkJoinWorkerThread queues except for the use of |
240 |
|
|
* submissionLock in method addSubmission. Unlike the case for |
241 |
|
|
* worker queues, multiple external threads can add new |
242 |
|
|
* submissions, so adding requires a lock. |
243 |
dl |
1.91 |
* |
244 |
|
|
* Compensation. Beyond work-stealing support and lifecycle |
245 |
|
|
* control, the main responsibility of this framework is to take |
246 |
|
|
* actions when one worker is waiting to join a task stolen (or |
247 |
|
|
* always held by) another. Because we are multiplexing many |
248 |
|
|
* tasks on to a pool of workers, we can't just let them block (as |
249 |
|
|
* in Thread.join). We also cannot just reassign the joiner's |
250 |
|
|
* run-time stack with another and replace it later, which would |
251 |
|
|
* be a form of "continuation", that even if possible is not |
252 |
|
|
* necessarily a good idea since we sometimes need both an |
253 |
|
|
* unblocked task and its continuation to progress. Instead we |
254 |
dl |
1.60 |
* combine two tactics: |
255 |
dl |
1.58 |
* |
256 |
dl |
1.60 |
* Helping: Arranging for the joiner to execute some task that it |
257 |
dl |
1.58 |
* would be running if the steal had not occurred. Method |
258 |
dl |
1.91 |
* ForkJoinWorkerThread.joinTask tracks joining->stealing |
259 |
dl |
1.58 |
* links to try to find such a task. |
260 |
|
|
* |
261 |
dl |
1.61 |
* Compensating: Unless there are already enough live threads, |
262 |
dl |
1.91 |
* method tryPreBlock() may create or re-activate a spare |
263 |
|
|
* thread to compensate for blocked joiners until they |
264 |
|
|
* unblock. |
265 |
|
|
* |
266 |
|
|
* The ManagedBlocker extension API can't use helping so relies |
267 |
|
|
* only on compensation in method awaitBlocker. |
268 |
dl |
1.58 |
* |
269 |
dl |
1.91 |
* It is impossible to keep exactly the target parallelism number |
270 |
|
|
* of threads running at any given time. Determining the |
271 |
dl |
1.66 |
* existence of conservatively safe helping targets, the |
272 |
|
|
* availability of already-created spares, and the apparent need |
273 |
|
|
* to create new spares are all racy and require heuristic |
274 |
dl |
1.91 |
* guidance, so we rely on multiple retries of each. Currently, |
275 |
|
|
* in keeping with on-demand signalling policy, we compensate only |
276 |
|
|
* if blocking would leave less than one active (non-waiting, |
277 |
|
|
* non-blocked) worker. Additionally, to avoid some false alarms |
278 |
|
|
* due to GC, lagging counters, system activity, etc, compensated |
279 |
dl |
1.95 |
* blocking for joins is only attempted after rechecks stabilize |
280 |
|
|
* (retries are interspersed with Thread.yield, for good |
281 |
|
|
* citizenship). The variable blockedCount, incremented before |
282 |
|
|
* blocking and decremented after, is sometimes needed to |
283 |
|
|
* distinguish cases of waiting for work vs blocking on joins or |
284 |
|
|
* other managed sync. Both cases are equivalent for most pool |
285 |
|
|
* control, so we can update non-atomically. (Additionally, |
286 |
|
|
* contention on blockedCount alleviates some contention on ctl). |
287 |
dl |
1.91 |
* |
288 |
|
|
* Shutdown and Termination. A call to shutdownNow atomically sets |
289 |
|
|
* the ctl stop bit and then (non-atomically) sets each workers |
290 |
|
|
* "terminate" status, cancels all unprocessed tasks, and wakes up |
291 |
|
|
* all waiting workers. Detecting whether termination should |
292 |
|
|
* commence after a non-abrupt shutdown() call requires more work |
293 |
jsr166 |
1.104 |
* and bookkeeping. We need consensus about quiescence (i.e., that |
294 |
dl |
1.91 |
* there is no more work) which is reflected in active counts so |
295 |
|
|
* long as there are no current blockers, as well as possible |
296 |
|
|
* re-evaluations during independent changes in blocking or |
297 |
|
|
* quiescing workers. |
298 |
dl |
1.58 |
* |
299 |
dl |
1.91 |
* Style notes: There is a lot of representation-level coupling |
300 |
dl |
1.53 |
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
301 |
dl |
1.91 |
* ForkJoinTask. Most fields of ForkJoinWorkerThread maintain |
302 |
|
|
* data structures managed by ForkJoinPool, so are directly |
303 |
|
|
* accessed. Conversely we allow access to "workers" array by |
304 |
dl |
1.53 |
* workers, and direct access to ForkJoinTask.status by both |
305 |
|
|
* ForkJoinPool and ForkJoinWorkerThread. There is little point |
306 |
|
|
* trying to reduce this, since any associated future changes in |
307 |
|
|
* representations will need to be accompanied by algorithmic |
308 |
dl |
1.91 |
* changes anyway. All together, these low-level implementation |
309 |
|
|
* choices produce as much as a factor of 4 performance |
310 |
|
|
* improvement compared to naive implementations, and enable the |
311 |
|
|
* processing of billions of tasks per second, at the expense of |
312 |
|
|
* some ugliness. |
313 |
|
|
* |
314 |
|
|
* Methods signalWork() and scan() are the main bottlenecks so are |
315 |
|
|
* especially heavily micro-optimized/mangled. There are lots of |
316 |
|
|
* inline assignments (of form "while ((local = field) != 0)") |
317 |
|
|
* which are usually the simplest way to ensure the required read |
318 |
|
|
* orderings (which are sometimes critical). This leads to a |
319 |
|
|
* "C"-like style of listing declarations of these locals at the |
320 |
|
|
* heads of methods or blocks. There are several occurrences of |
321 |
|
|
* the unusual "do {} while (!cas...)" which is the simplest way |
322 |
|
|
* to force an update of a CAS'ed variable. There are also other |
323 |
|
|
* coding oddities that help some methods perform reasonably even |
324 |
|
|
* when interpreted (not compiled). |
325 |
|
|
* |
326 |
|
|
* The order of declarations in this file is: (1) declarations of |
327 |
|
|
* statics (2) fields (along with constants used when unpacking |
328 |
|
|
* some of them), listed in an order that tends to reduce |
329 |
|
|
* contention among them a bit under most JVMs. (3) internal |
330 |
|
|
* control methods (4) callbacks and other support for |
331 |
|
|
* ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
332 |
|
|
* methods (plus a few little helpers). (6) static block |
333 |
|
|
* initializing all statics in a minimally dependent order. |
334 |
dl |
1.1 |
*/ |
335 |
|
|
|
336 |
|
|
/** |
337 |
jsr166 |
1.35 |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
338 |
|
|
* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
339 |
|
|
* for {@code ForkJoinWorkerThread} subclasses that extend base |
340 |
|
|
* functionality or initialize threads with different contexts. |
341 |
dl |
1.1 |
*/ |
342 |
|
|
public static interface ForkJoinWorkerThreadFactory { |
343 |
|
|
/** |
344 |
|
|
* Returns a new worker thread operating in the given pool. |
345 |
|
|
* |
346 |
|
|
* @param pool the pool this thread works in |
347 |
jsr166 |
1.48 |
* @throws NullPointerException if the pool is null |
348 |
dl |
1.1 |
*/ |
349 |
|
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
350 |
|
|
} |
351 |
|
|
|
352 |
|
|
/** |
353 |
jsr166 |
1.17 |
* Default ForkJoinWorkerThreadFactory implementation; creates a |
354 |
dl |
1.1 |
* new ForkJoinWorkerThread. |
355 |
|
|
*/ |
356 |
dl |
1.57 |
static class DefaultForkJoinWorkerThreadFactory |
357 |
dl |
1.1 |
implements ForkJoinWorkerThreadFactory { |
358 |
|
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
359 |
dl |
1.53 |
return new ForkJoinWorkerThread(pool); |
360 |
dl |
1.1 |
} |
361 |
|
|
} |
362 |
|
|
|
363 |
|
|
/** |
364 |
dl |
1.2 |
* Creates a new ForkJoinWorkerThread. This factory is used unless |
365 |
|
|
* overridden in ForkJoinPool constructors. |
366 |
dl |
1.1 |
*/ |
367 |
dl |
1.2 |
public static final ForkJoinWorkerThreadFactory |
368 |
dl |
1.91 |
defaultForkJoinWorkerThreadFactory; |
369 |
dl |
1.1 |
|
370 |
|
|
/** |
371 |
|
|
* Permission required for callers of methods that may start or |
372 |
|
|
* kill threads. |
373 |
|
|
*/ |
374 |
dl |
1.91 |
private static final RuntimePermission modifyThreadPermission; |
375 |
dl |
1.1 |
|
376 |
|
|
/** |
377 |
|
|
* If there is a security manager, makes sure caller has |
378 |
|
|
* permission to modify threads. |
379 |
|
|
*/ |
380 |
|
|
private static void checkPermission() { |
381 |
|
|
SecurityManager security = System.getSecurityManager(); |
382 |
|
|
if (security != null) |
383 |
|
|
security.checkPermission(modifyThreadPermission); |
384 |
|
|
} |
385 |
|
|
|
386 |
|
|
/** |
387 |
|
|
* Generator for assigning sequence numbers as pool names. |
388 |
|
|
*/ |
389 |
dl |
1.91 |
private static final AtomicInteger poolNumberGenerator; |
390 |
dl |
1.1 |
|
391 |
|
|
/** |
392 |
dl |
1.91 |
* Generator for initial random seeds for worker victim |
393 |
|
|
* selection. This is used only to create initial seeds. Random |
394 |
|
|
* steals use a cheaper xorshift generator per steal attempt. We |
395 |
|
|
* don't expect much contention on seedGenerator, so just use a |
396 |
|
|
* plain Random. |
397 |
dl |
1.66 |
*/ |
398 |
dl |
1.91 |
static final Random workerSeedGenerator; |
399 |
dl |
1.66 |
|
400 |
|
|
/** |
401 |
dl |
1.91 |
* Array holding all worker threads in the pool. Initialized upon |
402 |
|
|
* construction. Array size must be a power of two. Updates and |
403 |
|
|
* replacements are protected by scanGuard, but the array is |
404 |
|
|
* always kept in a consistent enough state to be randomly |
405 |
|
|
* accessed without locking by workers performing work-stealing, |
406 |
|
|
* as well as other traversal-based methods in this class, so long |
407 |
|
|
* as reads memory-acquire by first reading ctl. All readers must |
408 |
|
|
* tolerate that some array slots may be null. |
409 |
dl |
1.64 |
*/ |
410 |
dl |
1.91 |
ForkJoinWorkerThread[] workers; |
411 |
dl |
1.64 |
|
412 |
|
|
/** |
413 |
dl |
1.91 |
* Initial size for submission queue array. Must be a power of |
414 |
|
|
* two. In many applications, these always stay small so we use a |
415 |
|
|
* small initial cap. |
416 |
dl |
1.53 |
*/ |
417 |
dl |
1.91 |
private static final int INITIAL_QUEUE_CAPACITY = 8; |
418 |
dl |
1.53 |
|
419 |
|
|
/** |
420 |
dl |
1.91 |
* Maximum size for submission queue array. Must be a power of two |
421 |
|
|
* less than or equal to 1 << (31 - width of array entry) to |
422 |
|
|
* ensure lack of index wraparound, but is capped at a lower |
423 |
|
|
* value to help users trap runaway computations. |
424 |
dl |
1.1 |
*/ |
425 |
dl |
1.91 |
private static final int MAXIMUM_QUEUE_CAPACITY = 1 << 24; // 16M |
426 |
dl |
1.1 |
|
427 |
|
|
/** |
428 |
dl |
1.91 |
* Array serving as submission queue. Initialized upon construction. |
429 |
dl |
1.1 |
*/ |
430 |
dl |
1.91 |
private ForkJoinTask<?>[] submissionQueue; |
431 |
dl |
1.1 |
|
432 |
|
|
/** |
433 |
dl |
1.91 |
* Lock protecting submissions array for addSubmission |
434 |
dl |
1.1 |
*/ |
435 |
dl |
1.91 |
private final ReentrantLock submissionLock; |
436 |
dl |
1.1 |
|
437 |
|
|
/** |
438 |
dl |
1.91 |
* Condition for awaitTermination, using submissionLock for |
439 |
|
|
* convenience. |
440 |
dl |
1.1 |
*/ |
441 |
dl |
1.91 |
private final Condition termination; |
442 |
dl |
1.1 |
|
443 |
|
|
/** |
444 |
|
|
* Creation factory for worker threads. |
445 |
|
|
*/ |
446 |
|
|
private final ForkJoinWorkerThreadFactory factory; |
447 |
|
|
|
448 |
|
|
/** |
449 |
dl |
1.91 |
* The uncaught exception handler used when any worker abruptly |
450 |
|
|
* terminates. |
451 |
dl |
1.1 |
*/ |
452 |
dl |
1.91 |
final Thread.UncaughtExceptionHandler ueh; |
453 |
dl |
1.1 |
|
454 |
|
|
/** |
455 |
dl |
1.91 |
* Prefix for assigning names to worker threads |
456 |
dl |
1.1 |
*/ |
457 |
dl |
1.91 |
private final String workerNamePrefix; |
458 |
dl |
1.53 |
|
459 |
dl |
1.91 |
/** |
460 |
|
|
* Sum of per-thread steal counts, updated only when threads are |
461 |
|
|
* idle or terminating. |
462 |
|
|
*/ |
463 |
|
|
private volatile long stealCount; |
464 |
dl |
1.1 |
|
465 |
|
|
/** |
466 |
dl |
1.91 |
* Main pool control -- a long packed with: |
467 |
|
|
* AC: Number of active running workers minus target parallelism (16 bits) |
468 |
jsr166 |
1.106 |
* TC: Number of total workers minus target parallelism (16 bits) |
469 |
dl |
1.91 |
* ST: true if pool is terminating (1 bit) |
470 |
|
|
* EC: the wait count of top waiting thread (15 bits) |
471 |
|
|
* ID: ~poolIndex of top of Treiber stack of waiting threads (16 bits) |
472 |
|
|
* |
473 |
|
|
* When convenient, we can extract the upper 32 bits of counts and |
474 |
|
|
* the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e = |
475 |
|
|
* (int)ctl. The ec field is never accessed alone, but always |
476 |
|
|
* together with id and st. The offsets of counts by the target |
477 |
|
|
* parallelism and the positionings of fields makes it possible to |
478 |
|
|
* perform the most common checks via sign tests of fields: When |
479 |
|
|
* ac is negative, there are not enough active workers, when tc is |
480 |
|
|
* negative, there are not enough total workers, when id is |
481 |
|
|
* negative, there is at least one waiting worker, and when e is |
482 |
|
|
* negative, the pool is terminating. To deal with these possibly |
483 |
|
|
* negative fields, we use casts in and out of "short" and/or |
484 |
dl |
1.94 |
* signed shifts to maintain signedness. |
485 |
dl |
1.91 |
*/ |
486 |
|
|
volatile long ctl; |
487 |
|
|
|
488 |
|
|
// bit positions/shifts for fields |
489 |
|
|
private static final int AC_SHIFT = 48; |
490 |
|
|
private static final int TC_SHIFT = 32; |
491 |
|
|
private static final int ST_SHIFT = 31; |
492 |
|
|
private static final int EC_SHIFT = 16; |
493 |
|
|
|
494 |
|
|
// bounds |
495 |
|
|
private static final int MAX_ID = 0x7fff; // max poolIndex |
496 |
|
|
private static final int SMASK = 0xffff; // mask short bits |
497 |
|
|
private static final int SHORT_SIGN = 1 << 15; |
498 |
|
|
private static final int INT_SIGN = 1 << 31; |
499 |
|
|
|
500 |
|
|
// masks |
501 |
|
|
private static final long STOP_BIT = 0x0001L << ST_SHIFT; |
502 |
|
|
private static final long AC_MASK = ((long)SMASK) << AC_SHIFT; |
503 |
|
|
private static final long TC_MASK = ((long)SMASK) << TC_SHIFT; |
504 |
|
|
|
505 |
|
|
// units for incrementing and decrementing |
506 |
|
|
private static final long TC_UNIT = 1L << TC_SHIFT; |
507 |
|
|
private static final long AC_UNIT = 1L << AC_SHIFT; |
508 |
|
|
|
509 |
|
|
// masks and units for dealing with u = (int)(ctl >>> 32) |
510 |
|
|
private static final int UAC_SHIFT = AC_SHIFT - 32; |
511 |
|
|
private static final int UTC_SHIFT = TC_SHIFT - 32; |
512 |
|
|
private static final int UAC_MASK = SMASK << UAC_SHIFT; |
513 |
|
|
private static final int UTC_MASK = SMASK << UTC_SHIFT; |
514 |
|
|
private static final int UAC_UNIT = 1 << UAC_SHIFT; |
515 |
|
|
private static final int UTC_UNIT = 1 << UTC_SHIFT; |
516 |
|
|
|
517 |
|
|
// masks and units for dealing with e = (int)ctl |
518 |
|
|
private static final int E_MASK = 0x7fffffff; // no STOP_BIT |
519 |
|
|
private static final int EC_UNIT = 1 << EC_SHIFT; |
520 |
dl |
1.53 |
|
521 |
|
|
/** |
522 |
dl |
1.91 |
* The target parallelism level. |
523 |
dl |
1.61 |
*/ |
524 |
dl |
1.91 |
final int parallelism; |
525 |
dl |
1.61 |
|
526 |
|
|
/** |
527 |
dl |
1.91 |
* Index (mod submission queue length) of next element to take |
528 |
dl |
1.95 |
* from submission queue. Usage is identical to that for |
529 |
|
|
* per-worker queues -- see ForkJoinWorkerThread internal |
530 |
|
|
* documentation. |
531 |
dl |
1.53 |
*/ |
532 |
dl |
1.91 |
volatile int queueBase; |
533 |
dl |
1.1 |
|
534 |
|
|
/** |
535 |
dl |
1.91 |
* Index (mod submission queue length) of next element to add |
536 |
dl |
1.95 |
* in submission queue. Usage is identical to that for |
537 |
|
|
* per-worker queues -- see ForkJoinWorkerThread internal |
538 |
|
|
* documentation. |
539 |
dl |
1.53 |
*/ |
540 |
dl |
1.91 |
int queueTop; |
541 |
dl |
1.53 |
|
542 |
dl |
1.1 |
/** |
543 |
dl |
1.91 |
* True when shutdown() has been called. |
544 |
dl |
1.1 |
*/ |
545 |
dl |
1.91 |
volatile boolean shutdown; |
546 |
dl |
1.1 |
|
547 |
|
|
/** |
548 |
dl |
1.53 |
* True if use local fifo, not default lifo, for local polling |
549 |
dl |
1.57 |
* Read by, and replicated by ForkJoinWorkerThreads |
550 |
dl |
1.1 |
*/ |
551 |
dl |
1.57 |
final boolean locallyFifo; |
552 |
dl |
1.1 |
|
553 |
|
|
/** |
554 |
dl |
1.91 |
* The number of threads in ForkJoinWorkerThreads.helpQuiescePool. |
555 |
|
|
* When non-zero, suppresses automatic shutdown when active |
556 |
|
|
* counts become zero. |
557 |
dl |
1.1 |
*/ |
558 |
dl |
1.91 |
volatile int quiescerCount; |
559 |
dl |
1.6 |
|
560 |
|
|
/** |
561 |
dl |
1.91 |
* The number of threads blocked in join. |
562 |
dl |
1.1 |
*/ |
563 |
dl |
1.91 |
volatile int blockedCount; |
564 |
dl |
1.1 |
|
565 |
dl |
1.91 |
/** |
566 |
|
|
* Counter for worker Thread names (unrelated to their poolIndex) |
567 |
|
|
*/ |
568 |
|
|
private volatile int nextWorkerNumber; |
569 |
dl |
1.1 |
|
570 |
|
|
/** |
571 |
dl |
1.91 |
* The index for the next created worker. Accessed under scanGuard. |
572 |
dl |
1.1 |
*/ |
573 |
dl |
1.91 |
private int nextWorkerIndex; |
574 |
dl |
1.58 |
|
575 |
dl |
1.1 |
/** |
576 |
dl |
1.95 |
* SeqLock and index masking for updates to workers array. Locked |
577 |
|
|
* when SG_UNIT is set. Unlocking clears bit by adding |
578 |
dl |
1.91 |
* SG_UNIT. Staleness of read-only operations can be checked by |
579 |
|
|
* comparing scanGuard to value before the reads. The low 16 bits |
580 |
|
|
* (i.e, anding with SMASK) hold (the smallest power of two |
581 |
|
|
* covering all worker indices, minus one, and is used to avoid |
582 |
|
|
* dealing with large numbers of null slots when the workers array |
583 |
|
|
* is overallocated. |
584 |
dl |
1.85 |
*/ |
585 |
dl |
1.91 |
volatile int scanGuard; |
586 |
|
|
|
587 |
|
|
private static final int SG_UNIT = 1 << 16; |
588 |
dl |
1.85 |
|
589 |
|
|
/** |
590 |
dl |
1.91 |
* The wakeup interval (in nanoseconds) for a worker waiting for a |
591 |
|
|
* task when the pool is quiescent to instead try to shrink the |
592 |
|
|
* number of workers. The exact value does not matter too |
593 |
|
|
* much. It must be short enough to release resources during |
594 |
|
|
* sustained periods of idleness, but not so short that threads |
595 |
|
|
* are continually re-created. |
596 |
dl |
1.56 |
*/ |
597 |
dl |
1.91 |
private static final long SHRINK_RATE = |
598 |
|
|
4L * 1000L * 1000L * 1000L; // 4 seconds |
599 |
dl |
1.56 |
|
600 |
|
|
/** |
601 |
dl |
1.91 |
* Top-level loop for worker threads: On each step: if the |
602 |
|
|
* previous step swept through all queues and found no tasks, or |
603 |
|
|
* there are excess threads, then possibly blocks. Otherwise, |
604 |
|
|
* scans for and, if found, executes a task. Returns when pool |
605 |
|
|
* and/or worker terminate. |
606 |
dl |
1.61 |
* |
607 |
dl |
1.91 |
* @param w the worker |
608 |
dl |
1.58 |
*/ |
609 |
dl |
1.91 |
final void work(ForkJoinWorkerThread w) { |
610 |
|
|
boolean swept = false; // true on empty scans |
611 |
|
|
long c; |
612 |
|
|
while (!w.terminate && (int)(c = ctl) >= 0) { |
613 |
|
|
int a; // active count |
614 |
|
|
if (!swept && (a = (int)(c >> AC_SHIFT)) <= 0) |
615 |
|
|
swept = scan(w, a); |
616 |
|
|
else if (tryAwaitWork(w, c)) |
617 |
|
|
swept = false; |
618 |
dl |
1.61 |
} |
619 |
|
|
} |
620 |
|
|
|
621 |
dl |
1.91 |
// Signalling |
622 |
|
|
|
623 |
dl |
1.61 |
/** |
624 |
dl |
1.91 |
* Wakes up or creates a worker. |
625 |
dl |
1.53 |
*/ |
626 |
dl |
1.91 |
final void signalWork() { |
627 |
|
|
/* |
628 |
|
|
* The while condition is true if: (there is are too few total |
629 |
|
|
* workers OR there is at least one waiter) AND (there are too |
630 |
|
|
* few active workers OR the pool is terminating). The value |
631 |
|
|
* of e distinguishes the remaining cases: zero (no waiters) |
632 |
|
|
* for create, negative if terminating (in which case do |
633 |
|
|
* nothing), else release a waiter. The secondary checks for |
634 |
|
|
* release (non-null array etc) can fail if the pool begins |
635 |
|
|
* terminating after the test, and don't impose any added cost |
636 |
|
|
* because JVMs must perform null and bounds checks anyway. |
637 |
|
|
*/ |
638 |
|
|
long c; int e, u; |
639 |
|
|
while ((((e = (int)(c = ctl)) | (u = (int)(c >>> 32))) & |
640 |
|
|
(INT_SIGN|SHORT_SIGN)) == (INT_SIGN|SHORT_SIGN) && e >= 0) { |
641 |
|
|
if (e > 0) { // release a waiting worker |
642 |
|
|
int i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws; |
643 |
|
|
if ((ws = workers) == null || |
644 |
|
|
(i = ~e & SMASK) >= ws.length || |
645 |
|
|
(w = ws[i]) == null) |
646 |
|
|
break; |
647 |
|
|
long nc = (((long)(w.nextWait & E_MASK)) | |
648 |
|
|
((long)(u + UAC_UNIT) << 32)); |
649 |
|
|
if (w.eventCount == e && |
650 |
|
|
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
651 |
|
|
w.eventCount = (e + EC_UNIT) & E_MASK; |
652 |
|
|
if (w.parked) |
653 |
|
|
UNSAFE.unpark(w); |
654 |
|
|
break; |
655 |
|
|
} |
656 |
|
|
} |
657 |
|
|
else if (UNSAFE.compareAndSwapLong |
658 |
|
|
(this, ctlOffset, c, |
659 |
|
|
(long)(((u + UTC_UNIT) & UTC_MASK) | |
660 |
|
|
((u + UAC_UNIT) & UAC_MASK)) << 32)) { |
661 |
|
|
addWorker(); |
662 |
|
|
break; |
663 |
|
|
} |
664 |
|
|
} |
665 |
dl |
1.53 |
} |
666 |
|
|
|
667 |
|
|
/** |
668 |
dl |
1.91 |
* Variant of signalWork to help release waiters on rescans. |
669 |
|
|
* Tries once to release a waiter if active count < 0. |
670 |
|
|
* |
671 |
|
|
* @return false if failed due to contention, else true |
672 |
dl |
1.53 |
*/ |
673 |
dl |
1.91 |
private boolean tryReleaseWaiter() { |
674 |
|
|
long c; int e, i; ForkJoinWorkerThread w; ForkJoinWorkerThread[] ws; |
675 |
|
|
if ((e = (int)(c = ctl)) > 0 && |
676 |
|
|
(int)(c >> AC_SHIFT) < 0 && |
677 |
|
|
(ws = workers) != null && |
678 |
|
|
(i = ~e & SMASK) < ws.length && |
679 |
|
|
(w = ws[i]) != null) { |
680 |
|
|
long nc = ((long)(w.nextWait & E_MASK) | |
681 |
|
|
((c + AC_UNIT) & (AC_MASK|TC_MASK))); |
682 |
|
|
if (w.eventCount != e || |
683 |
|
|
!UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) |
684 |
dl |
1.53 |
return false; |
685 |
dl |
1.91 |
w.eventCount = (e + EC_UNIT) & E_MASK; |
686 |
|
|
if (w.parked) |
687 |
|
|
UNSAFE.unpark(w); |
688 |
dl |
1.53 |
} |
689 |
dl |
1.91 |
return true; |
690 |
dl |
1.53 |
} |
691 |
|
|
|
692 |
dl |
1.91 |
// Scanning for tasks |
693 |
dl |
1.53 |
|
694 |
|
|
/** |
695 |
dl |
1.91 |
* Scans for and, if found, executes one task. Scans start at a |
696 |
|
|
* random index of workers array, and randomly select the first |
697 |
|
|
* (2*#workers)-1 probes, and then, if all empty, resort to 2 |
698 |
|
|
* circular sweeps, which is necessary to check quiescence. and |
699 |
|
|
* taking a submission only if no stealable tasks were found. The |
700 |
|
|
* steal code inside the loop is a specialized form of |
701 |
|
|
* ForkJoinWorkerThread.deqTask, followed bookkeeping to support |
702 |
|
|
* helpJoinTask and signal propagation. The code for submission |
703 |
|
|
* queues is almost identical. On each steal, the worker completes |
704 |
|
|
* not only the task, but also all local tasks that this task may |
705 |
|
|
* have generated. On detecting staleness or contention when |
706 |
|
|
* trying to take a task, this method returns without finishing |
707 |
|
|
* sweep, which allows global state rechecks before retry. |
708 |
|
|
* |
709 |
|
|
* @param w the worker |
710 |
|
|
* @param a the number of active workers |
711 |
|
|
* @return true if swept all queues without finding a task |
712 |
dl |
1.53 |
*/ |
713 |
dl |
1.91 |
private boolean scan(ForkJoinWorkerThread w, int a) { |
714 |
|
|
int g = scanGuard; // mask 0 avoids useless scans if only one active |
715 |
dl |
1.96 |
int m = (parallelism == 1 - a && blockedCount == 0) ? 0 : g & SMASK; |
716 |
dl |
1.91 |
ForkJoinWorkerThread[] ws = workers; |
717 |
|
|
if (ws == null || ws.length <= m) // staleness check |
718 |
|
|
return false; |
719 |
|
|
for (int r = w.seed, k = r, j = -(m + m); j <= m + m; ++j) { |
720 |
|
|
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
721 |
|
|
ForkJoinWorkerThread v = ws[k & m]; |
722 |
|
|
if (v != null && (b = v.queueBase) != v.queueTop && |
723 |
|
|
(q = v.queue) != null && (i = (q.length - 1) & b) >= 0) { |
724 |
|
|
long u = (i << ASHIFT) + ABASE; |
725 |
|
|
if ((t = q[i]) != null && v.queueBase == b && |
726 |
|
|
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
727 |
|
|
int d = (v.queueBase = b + 1) - v.queueTop; |
728 |
|
|
v.stealHint = w.poolIndex; |
729 |
|
|
if (d != 0) |
730 |
|
|
signalWork(); // propagate if nonempty |
731 |
|
|
w.execTask(t); |
732 |
|
|
} |
733 |
|
|
r ^= r << 13; r ^= r >>> 17; w.seed = r ^ (r << 5); |
734 |
|
|
return false; // store next seed |
735 |
|
|
} |
736 |
|
|
else if (j < 0) { // xorshift |
737 |
|
|
r ^= r << 13; r ^= r >>> 17; k = r ^= r << 5; |
738 |
|
|
} |
739 |
|
|
else |
740 |
|
|
++k; |
741 |
|
|
} |
742 |
|
|
if (scanGuard != g) // staleness check |
743 |
|
|
return false; |
744 |
|
|
else { // try to take submission |
745 |
|
|
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
746 |
|
|
if ((b = queueBase) != queueTop && |
747 |
|
|
(q = submissionQueue) != null && |
748 |
|
|
(i = (q.length - 1) & b) >= 0) { |
749 |
|
|
long u = (i << ASHIFT) + ABASE; |
750 |
|
|
if ((t = q[i]) != null && queueBase == b && |
751 |
|
|
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
752 |
|
|
queueBase = b + 1; |
753 |
|
|
w.execTask(t); |
754 |
|
|
} |
755 |
|
|
return false; |
756 |
|
|
} |
757 |
|
|
return true; // all queues empty |
758 |
dl |
1.53 |
} |
759 |
|
|
} |
760 |
|
|
|
761 |
|
|
/** |
762 |
dl |
1.93 |
* Tries to enqueue worker w in wait queue and await change in |
763 |
dl |
1.100 |
* worker's eventCount. If the pool is quiescent and there is |
764 |
|
|
* more than one worker, possibly terminates worker upon exit. |
765 |
|
|
* Otherwise, before blocking, rescans queues to avoid missed |
766 |
|
|
* signals. Upon finding work, releases at least one worker |
767 |
|
|
* (which may be the current worker). Rescans restart upon |
768 |
|
|
* detected staleness or failure to release due to |
769 |
|
|
* contention. Note the unusual conventions about Thread.interrupt |
770 |
|
|
* here and elsewhere: Because interrupts are used solely to alert |
771 |
|
|
* threads to check termination, which is checked here anyway, we |
772 |
|
|
* clear status (using Thread.interrupted) before any call to |
773 |
|
|
* park, so that park does not immediately return due to status |
774 |
|
|
* being set via some other unrelated call to interrupt in user |
775 |
|
|
* code. |
776 |
dl |
1.91 |
* |
777 |
|
|
* @param w the calling worker |
778 |
|
|
* @param c the ctl value on entry |
779 |
|
|
* @return true if waited or another thread was released upon enq |
780 |
dl |
1.53 |
*/ |
781 |
dl |
1.91 |
private boolean tryAwaitWork(ForkJoinWorkerThread w, long c) { |
782 |
|
|
int v = w.eventCount; |
783 |
dl |
1.93 |
w.nextWait = (int)c; // w's successor record |
784 |
dl |
1.91 |
long nc = (long)(v & E_MASK) | ((c - AC_UNIT) & (AC_MASK|TC_MASK)); |
785 |
|
|
if (ctl != c || !UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
786 |
dl |
1.93 |
long d = ctl; // return true if lost to a deq, to force scan |
787 |
dl |
1.91 |
return (int)d != (int)c && ((d - c) & AC_MASK) >= 0L; |
788 |
|
|
} |
789 |
dl |
1.93 |
for (int sc = w.stealCount; sc != 0;) { // accumulate stealCount |
790 |
|
|
long s = stealCount; |
791 |
|
|
if (UNSAFE.compareAndSwapLong(this, stealCountOffset, s, s + sc)) |
792 |
|
|
sc = w.stealCount = 0; |
793 |
|
|
else if (w.eventCount != v) |
794 |
|
|
return true; // update next time |
795 |
|
|
} |
796 |
dl |
1.101 |
if ((!shutdown || !tryTerminate(false)) && |
797 |
|
|
(int)c != 0 && parallelism + (int)(nc >> AC_SHIFT) == 0 && |
798 |
dl |
1.92 |
blockedCount == 0 && quiescerCount == 0) |
799 |
dl |
1.93 |
idleAwaitWork(w, nc, c, v); // quiescent |
800 |
|
|
for (boolean rescanned = false;;) { |
801 |
dl |
1.91 |
if (w.eventCount != v) |
802 |
|
|
return true; |
803 |
dl |
1.93 |
if (!rescanned) { |
804 |
dl |
1.91 |
int g = scanGuard, m = g & SMASK; |
805 |
|
|
ForkJoinWorkerThread[] ws = workers; |
806 |
|
|
if (ws != null && m < ws.length) { |
807 |
|
|
rescanned = true; |
808 |
|
|
for (int i = 0; i <= m; ++i) { |
809 |
|
|
ForkJoinWorkerThread u = ws[i]; |
810 |
|
|
if (u != null) { |
811 |
|
|
if (u.queueBase != u.queueTop && |
812 |
|
|
!tryReleaseWaiter()) |
813 |
|
|
rescanned = false; // contended |
814 |
|
|
if (w.eventCount != v) |
815 |
|
|
return true; |
816 |
|
|
} |
817 |
|
|
} |
818 |
|
|
} |
819 |
|
|
if (scanGuard != g || // stale |
820 |
|
|
(queueBase != queueTop && !tryReleaseWaiter())) |
821 |
|
|
rescanned = false; |
822 |
|
|
if (!rescanned) |
823 |
|
|
Thread.yield(); // reduce contention |
824 |
|
|
else |
825 |
|
|
Thread.interrupted(); // clear before park |
826 |
|
|
} |
827 |
|
|
else { |
828 |
|
|
w.parked = true; // must recheck |
829 |
|
|
if (w.eventCount != v) { |
830 |
|
|
w.parked = false; |
831 |
|
|
return true; |
832 |
|
|
} |
833 |
|
|
LockSupport.park(this); |
834 |
|
|
rescanned = w.parked = false; |
835 |
|
|
} |
836 |
dl |
1.53 |
} |
837 |
|
|
} |
838 |
|
|
|
839 |
|
|
/** |
840 |
dl |
1.93 |
* If inactivating worker w has caused pool to become |
841 |
|
|
* quiescent, check for pool termination, and wait for event |
842 |
|
|
* for up to SHRINK_RATE nanosecs (rescans are unnecessary in |
843 |
|
|
* this case because quiescence reflects consensus about lack |
844 |
|
|
* of work). On timeout, if ctl has not changed, terminate the |
845 |
|
|
* worker. Upon its termination (see deregisterWorker), it may |
846 |
|
|
* wake up another worker to possibly repeat this process. |
847 |
dl |
1.91 |
* |
848 |
|
|
* @param w the calling worker |
849 |
dl |
1.93 |
* @param currentCtl the ctl value after enqueuing w |
850 |
|
|
* @param prevCtl the ctl value if w terminated |
851 |
|
|
* @param v the eventCount w awaits change |
852 |
|
|
*/ |
853 |
|
|
private void idleAwaitWork(ForkJoinWorkerThread w, long currentCtl, |
854 |
|
|
long prevCtl, int v) { |
855 |
|
|
if (w.eventCount == v) { |
856 |
|
|
if (shutdown) |
857 |
|
|
tryTerminate(false); |
858 |
|
|
ForkJoinTask.helpExpungeStaleExceptions(); // help clean weak refs |
859 |
|
|
while (ctl == currentCtl) { |
860 |
|
|
long startTime = System.nanoTime(); |
861 |
dl |
1.91 |
w.parked = true; |
862 |
dl |
1.93 |
if (w.eventCount == v) // must recheck |
863 |
dl |
1.91 |
LockSupport.parkNanos(this, SHRINK_RATE); |
864 |
|
|
w.parked = false; |
865 |
dl |
1.93 |
if (w.eventCount != v) |
866 |
|
|
break; |
867 |
jsr166 |
1.102 |
else if (System.nanoTime() - startTime < |
868 |
dl |
1.99 |
SHRINK_RATE - (SHRINK_RATE / 10)) // timing slop |
869 |
dl |
1.93 |
Thread.interrupted(); // spurious wakeup |
870 |
|
|
else if (UNSAFE.compareAndSwapLong(this, ctlOffset, |
871 |
|
|
currentCtl, prevCtl)) { |
872 |
|
|
w.terminate = true; // restore previous |
873 |
|
|
w.eventCount = ((int)currentCtl + EC_UNIT) & E_MASK; |
874 |
|
|
break; |
875 |
dl |
1.91 |
} |
876 |
|
|
} |
877 |
|
|
} |
878 |
dl |
1.53 |
} |
879 |
|
|
|
880 |
dl |
1.91 |
// Submissions |
881 |
dl |
1.53 |
|
882 |
|
|
/** |
883 |
dl |
1.91 |
* Enqueues the given task in the submissionQueue. Same idea as |
884 |
|
|
* ForkJoinWorkerThread.pushTask except for use of submissionLock. |
885 |
|
|
* |
886 |
|
|
* @param t the task |
887 |
dl |
1.53 |
*/ |
888 |
dl |
1.91 |
private void addSubmission(ForkJoinTask<?> t) { |
889 |
|
|
final ReentrantLock lock = this.submissionLock; |
890 |
|
|
lock.lock(); |
891 |
|
|
try { |
892 |
|
|
ForkJoinTask<?>[] q; int s, m; |
893 |
|
|
if ((q = submissionQueue) != null) { // ignore if queue removed |
894 |
|
|
long u = (((s = queueTop) & (m = q.length-1)) << ASHIFT)+ABASE; |
895 |
|
|
UNSAFE.putOrderedObject(q, u, t); |
896 |
|
|
queueTop = s + 1; |
897 |
|
|
if (s - queueBase == m) |
898 |
|
|
growSubmissionQueue(); |
899 |
dl |
1.66 |
} |
900 |
dl |
1.91 |
} finally { |
901 |
|
|
lock.unlock(); |
902 |
dl |
1.53 |
} |
903 |
dl |
1.91 |
signalWork(); |
904 |
dl |
1.53 |
} |
905 |
|
|
|
906 |
dl |
1.91 |
// (pollSubmission is defined below with exported methods) |
907 |
|
|
|
908 |
dl |
1.53 |
/** |
909 |
dl |
1.91 |
* Creates or doubles submissionQueue array. |
910 |
dl |
1.95 |
* Basically identical to ForkJoinWorkerThread version. |
911 |
dl |
1.53 |
*/ |
912 |
dl |
1.91 |
private void growSubmissionQueue() { |
913 |
|
|
ForkJoinTask<?>[] oldQ = submissionQueue; |
914 |
|
|
int size = oldQ != null ? oldQ.length << 1 : INITIAL_QUEUE_CAPACITY; |
915 |
|
|
if (size > MAXIMUM_QUEUE_CAPACITY) |
916 |
|
|
throw new RejectedExecutionException("Queue capacity exceeded"); |
917 |
|
|
if (size < INITIAL_QUEUE_CAPACITY) |
918 |
|
|
size = INITIAL_QUEUE_CAPACITY; |
919 |
|
|
ForkJoinTask<?>[] q = submissionQueue = new ForkJoinTask<?>[size]; |
920 |
|
|
int mask = size - 1; |
921 |
|
|
int top = queueTop; |
922 |
|
|
int oldMask; |
923 |
|
|
if (oldQ != null && (oldMask = oldQ.length - 1) >= 0) { |
924 |
|
|
for (int b = queueBase; b != top; ++b) { |
925 |
|
|
long u = ((b & oldMask) << ASHIFT) + ABASE; |
926 |
|
|
Object x = UNSAFE.getObjectVolatile(oldQ, u); |
927 |
|
|
if (x != null && UNSAFE.compareAndSwapObject(oldQ, u, x, null)) |
928 |
|
|
UNSAFE.putObjectVolatile |
929 |
|
|
(q, ((b & mask) << ASHIFT) + ABASE, x); |
930 |
dl |
1.64 |
} |
931 |
|
|
} |
932 |
|
|
} |
933 |
|
|
|
934 |
dl |
1.91 |
// Blocking support |
935 |
|
|
|
936 |
dl |
1.64 |
/** |
937 |
dl |
1.91 |
* Tries to increment blockedCount, decrement active count |
938 |
|
|
* (sometimes implicitly) and possibly release or create a |
939 |
|
|
* compensating worker in preparation for blocking. Fails |
940 |
|
|
* on contention or termination. |
941 |
|
|
* |
942 |
|
|
* @return true if the caller can block, else should recheck and retry |
943 |
|
|
*/ |
944 |
|
|
private boolean tryPreBlock() { |
945 |
|
|
int b = blockedCount; |
946 |
|
|
if (UNSAFE.compareAndSwapInt(this, blockedCountOffset, b, b + 1)) { |
947 |
|
|
int pc = parallelism; |
948 |
|
|
do { |
949 |
|
|
ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w; |
950 |
jsr166 |
1.105 |
int e, ac, tc, i; |
951 |
dl |
1.91 |
long c = ctl; |
952 |
|
|
int u = (int)(c >>> 32); |
953 |
|
|
if ((e = (int)c) < 0) { |
954 |
|
|
// skip -- terminating |
955 |
|
|
} |
956 |
|
|
else if ((ac = (u >> UAC_SHIFT)) <= 0 && e != 0 && |
957 |
|
|
(ws = workers) != null && |
958 |
|
|
(i = ~e & SMASK) < ws.length && |
959 |
|
|
(w = ws[i]) != null) { |
960 |
|
|
long nc = ((long)(w.nextWait & E_MASK) | |
961 |
|
|
(c & (AC_MASK|TC_MASK))); |
962 |
|
|
if (w.eventCount == e && |
963 |
|
|
UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
964 |
|
|
w.eventCount = (e + EC_UNIT) & E_MASK; |
965 |
|
|
if (w.parked) |
966 |
|
|
UNSAFE.unpark(w); |
967 |
|
|
return true; // release an idle worker |
968 |
|
|
} |
969 |
|
|
} |
970 |
|
|
else if ((tc = (short)(u >>> UTC_SHIFT)) >= 0 && ac + pc > 1) { |
971 |
|
|
long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK); |
972 |
|
|
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) |
973 |
|
|
return true; // no compensation needed |
974 |
|
|
} |
975 |
|
|
else if (tc + pc < MAX_ID) { |
976 |
|
|
long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK); |
977 |
|
|
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, nc)) { |
978 |
|
|
addWorker(); |
979 |
|
|
return true; // create a replacement |
980 |
|
|
} |
981 |
dl |
1.61 |
} |
982 |
dl |
1.91 |
// try to back out on any failure and let caller retry |
983 |
|
|
} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset, |
984 |
|
|
b = blockedCount, b - 1)); |
985 |
dl |
1.53 |
} |
986 |
dl |
1.91 |
return false; |
987 |
dl |
1.64 |
} |
988 |
|
|
|
989 |
dl |
1.91 |
/** |
990 |
jsr166 |
1.105 |
* Decrements blockedCount and increments active count. |
991 |
dl |
1.91 |
*/ |
992 |
|
|
private void postBlock() { |
993 |
|
|
long c; |
994 |
|
|
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, // no mask |
995 |
|
|
c = ctl, c + AC_UNIT)); |
996 |
|
|
int b; |
997 |
jsr166 |
1.102 |
do {} while (!UNSAFE.compareAndSwapInt(this, blockedCountOffset, |
998 |
|
|
b = blockedCount, b - 1)); |
999 |
dl |
1.91 |
} |
1000 |
dl |
1.61 |
|
1001 |
|
|
/** |
1002 |
dl |
1.91 |
* Possibly blocks waiting for the given task to complete, or |
1003 |
|
|
* cancels the task if terminating. Fails to wait if contended. |
1004 |
|
|
* |
1005 |
|
|
* @param joinMe the task |
1006 |
dl |
1.61 |
*/ |
1007 |
dl |
1.91 |
final void tryAwaitJoin(ForkJoinTask<?> joinMe) { |
1008 |
|
|
Thread.interrupted(); // clear interrupts before checking termination |
1009 |
|
|
if (joinMe.status >= 0) { |
1010 |
|
|
if (tryPreBlock()) { |
1011 |
|
|
joinMe.tryAwaitDone(0L); |
1012 |
|
|
postBlock(); |
1013 |
|
|
} |
1014 |
dl |
1.95 |
else if ((ctl & STOP_BIT) != 0L) |
1015 |
dl |
1.91 |
joinMe.cancelIgnoringExceptions(); |
1016 |
|
|
} |
1017 |
dl |
1.61 |
} |
1018 |
|
|
|
1019 |
|
|
/** |
1020 |
dl |
1.91 |
* Possibly blocks the given worker waiting for joinMe to |
1021 |
jsr166 |
1.105 |
* complete or timeout. |
1022 |
dl |
1.91 |
* |
1023 |
|
|
* @param joinMe the task |
1024 |
|
|
* @param millis the wait time for underlying Object.wait |
1025 |
dl |
1.61 |
*/ |
1026 |
dl |
1.91 |
final void timedAwaitJoin(ForkJoinTask<?> joinMe, long nanos) { |
1027 |
|
|
while (joinMe.status >= 0) { |
1028 |
|
|
Thread.interrupted(); |
1029 |
|
|
if ((ctl & STOP_BIT) != 0L) { |
1030 |
|
|
joinMe.cancelIgnoringExceptions(); |
1031 |
|
|
break; |
1032 |
|
|
} |
1033 |
|
|
if (tryPreBlock()) { |
1034 |
|
|
long last = System.nanoTime(); |
1035 |
|
|
while (joinMe.status >= 0) { |
1036 |
|
|
long millis = TimeUnit.NANOSECONDS.toMillis(nanos); |
1037 |
|
|
if (millis <= 0) |
1038 |
|
|
break; |
1039 |
|
|
joinMe.tryAwaitDone(millis); |
1040 |
|
|
if (joinMe.status < 0) |
1041 |
|
|
break; |
1042 |
|
|
if ((ctl & STOP_BIT) != 0L) { |
1043 |
|
|
joinMe.cancelIgnoringExceptions(); |
1044 |
|
|
break; |
1045 |
|
|
} |
1046 |
|
|
long now = System.nanoTime(); |
1047 |
|
|
nanos -= now - last; |
1048 |
|
|
last = now; |
1049 |
|
|
} |
1050 |
|
|
postBlock(); |
1051 |
|
|
break; |
1052 |
|
|
} |
1053 |
dl |
1.64 |
} |
1054 |
|
|
} |
1055 |
|
|
|
1056 |
|
|
/** |
1057 |
jsr166 |
1.105 |
* If necessary, compensates for blocker, and blocks. |
1058 |
dl |
1.64 |
*/ |
1059 |
dl |
1.91 |
private void awaitBlocker(ManagedBlocker blocker) |
1060 |
|
|
throws InterruptedException { |
1061 |
|
|
while (!blocker.isReleasable()) { |
1062 |
|
|
if (tryPreBlock()) { |
1063 |
dl |
1.66 |
try { |
1064 |
dl |
1.91 |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1065 |
|
|
} finally { |
1066 |
|
|
postBlock(); |
1067 |
dl |
1.66 |
} |
1068 |
dl |
1.91 |
break; |
1069 |
dl |
1.64 |
} |
1070 |
|
|
} |
1071 |
|
|
} |
1072 |
|
|
|
1073 |
dl |
1.91 |
// Creating, registering and deregistring workers |
1074 |
|
|
|
1075 |
dl |
1.64 |
/** |
1076 |
dl |
1.91 |
* Tries to create and start a worker; minimally rolls back counts |
1077 |
|
|
* on failure. |
1078 |
dl |
1.64 |
*/ |
1079 |
dl |
1.91 |
private void addWorker() { |
1080 |
|
|
Throwable ex = null; |
1081 |
|
|
ForkJoinWorkerThread t = null; |
1082 |
|
|
try { |
1083 |
|
|
t = factory.newThread(this); |
1084 |
|
|
} catch (Throwable e) { |
1085 |
|
|
ex = e; |
1086 |
|
|
} |
1087 |
|
|
if (t == null) { // null or exceptional factory return |
1088 |
|
|
long c; // adjust counts |
1089 |
|
|
do {} while (!UNSAFE.compareAndSwapLong |
1090 |
|
|
(this, ctlOffset, c = ctl, |
1091 |
|
|
(((c - AC_UNIT) & AC_MASK) | |
1092 |
|
|
((c - TC_UNIT) & TC_MASK) | |
1093 |
|
|
(c & ~(AC_MASK|TC_MASK))))); |
1094 |
|
|
// Propagate exception if originating from an external caller |
1095 |
|
|
if (!tryTerminate(false) && ex != null && |
1096 |
|
|
!(Thread.currentThread() instanceof ForkJoinWorkerThread)) |
1097 |
|
|
UNSAFE.throwException(ex); |
1098 |
|
|
} |
1099 |
|
|
else |
1100 |
|
|
t.start(); |
1101 |
dl |
1.61 |
} |
1102 |
|
|
|
1103 |
dl |
1.53 |
/** |
1104 |
dl |
1.91 |
* Callback from ForkJoinWorkerThread constructor to assign a |
1105 |
|
|
* public name |
1106 |
dl |
1.53 |
*/ |
1107 |
dl |
1.91 |
final String nextWorkerName() { |
1108 |
|
|
for (int n;;) { |
1109 |
|
|
if (UNSAFE.compareAndSwapInt(this, nextWorkerNumberOffset, |
1110 |
|
|
n = nextWorkerNumber, ++n)) |
1111 |
|
|
return workerNamePrefix + n; |
1112 |
dl |
1.53 |
} |
1113 |
|
|
} |
1114 |
|
|
|
1115 |
|
|
/** |
1116 |
dl |
1.91 |
* Callback from ForkJoinWorkerThread constructor to |
1117 |
|
|
* determine its poolIndex and record in workers array. |
1118 |
dl |
1.56 |
* |
1119 |
dl |
1.91 |
* @param w the worker |
1120 |
|
|
* @return the worker's pool index |
1121 |
dl |
1.53 |
*/ |
1122 |
dl |
1.91 |
final int registerWorker(ForkJoinWorkerThread w) { |
1123 |
|
|
/* |
1124 |
|
|
* In the typical case, a new worker acquires the lock, uses |
1125 |
|
|
* next available index and returns quickly. Since we should |
1126 |
|
|
* not block callers (ultimately from signalWork or |
1127 |
|
|
* tryPreBlock) waiting for the lock needed to do this, we |
1128 |
|
|
* instead help release other workers while waiting for the |
1129 |
|
|
* lock. |
1130 |
|
|
*/ |
1131 |
|
|
for (int g;;) { |
1132 |
|
|
ForkJoinWorkerThread[] ws; |
1133 |
|
|
if (((g = scanGuard) & SG_UNIT) == 0 && |
1134 |
|
|
UNSAFE.compareAndSwapInt(this, scanGuardOffset, |
1135 |
|
|
g, g | SG_UNIT)) { |
1136 |
|
|
int k = nextWorkerIndex; |
1137 |
|
|
try { |
1138 |
|
|
if ((ws = workers) != null) { // ignore on shutdown |
1139 |
|
|
int n = ws.length; |
1140 |
|
|
if (k < 0 || k >= n || ws[k] != null) { |
1141 |
|
|
for (k = 0; k < n && ws[k] != null; ++k) |
1142 |
|
|
; |
1143 |
|
|
if (k == n) |
1144 |
|
|
ws = workers = Arrays.copyOf(ws, n << 1); |
1145 |
|
|
} |
1146 |
|
|
ws[k] = w; |
1147 |
|
|
nextWorkerIndex = k + 1; |
1148 |
|
|
int m = g & SMASK; |
1149 |
jsr166 |
1.102 |
g = (k > m) ? ((m << 1) + 1) & SMASK : g + (SG_UNIT<<1); |
1150 |
dl |
1.91 |
} |
1151 |
|
|
} finally { |
1152 |
|
|
scanGuard = g; |
1153 |
|
|
} |
1154 |
|
|
return k; |
1155 |
dl |
1.82 |
} |
1156 |
dl |
1.91 |
else if ((ws = workers) != null) { // help release others |
1157 |
|
|
for (ForkJoinWorkerThread u : ws) { |
1158 |
|
|
if (u != null && u.queueBase != u.queueTop) { |
1159 |
|
|
if (tryReleaseWaiter()) |
1160 |
dl |
1.85 |
break; |
1161 |
dl |
1.83 |
} |
1162 |
|
|
} |
1163 |
dl |
1.53 |
} |
1164 |
|
|
} |
1165 |
|
|
} |
1166 |
|
|
|
1167 |
|
|
/** |
1168 |
dl |
1.91 |
* Final callback from terminating worker. Removes record of |
1169 |
|
|
* worker from array, and adjusts counts. If pool is shutting |
1170 |
|
|
* down, tries to complete termination. |
1171 |
|
|
* |
1172 |
|
|
* @param w the worker |
1173 |
dl |
1.53 |
*/ |
1174 |
dl |
1.91 |
final void deregisterWorker(ForkJoinWorkerThread w, Throwable ex) { |
1175 |
|
|
int idx = w.poolIndex; |
1176 |
|
|
int sc = w.stealCount; |
1177 |
|
|
int steps = 0; |
1178 |
|
|
// Remove from array, adjust worker counts and collect steal count. |
1179 |
|
|
// We can intermix failed removes or adjusts with steal updates |
1180 |
|
|
do { |
1181 |
|
|
long s, c; |
1182 |
|
|
int g; |
1183 |
|
|
if (steps == 0 && ((g = scanGuard) & SG_UNIT) == 0 && |
1184 |
|
|
UNSAFE.compareAndSwapInt(this, scanGuardOffset, |
1185 |
|
|
g, g |= SG_UNIT)) { |
1186 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1187 |
|
|
if (ws != null && idx >= 0 && |
1188 |
|
|
idx < ws.length && ws[idx] == w) |
1189 |
|
|
ws[idx] = null; // verify |
1190 |
|
|
nextWorkerIndex = idx; |
1191 |
|
|
scanGuard = g + SG_UNIT; |
1192 |
|
|
steps = 1; |
1193 |
dl |
1.60 |
} |
1194 |
dl |
1.91 |
if (steps == 1 && |
1195 |
|
|
UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl, |
1196 |
|
|
(((c - AC_UNIT) & AC_MASK) | |
1197 |
|
|
((c - TC_UNIT) & TC_MASK) | |
1198 |
|
|
(c & ~(AC_MASK|TC_MASK))))) |
1199 |
|
|
steps = 2; |
1200 |
|
|
if (sc != 0 && |
1201 |
|
|
UNSAFE.compareAndSwapLong(this, stealCountOffset, |
1202 |
|
|
s = stealCount, s + sc)) |
1203 |
|
|
sc = 0; |
1204 |
|
|
} while (steps != 2 || sc != 0); |
1205 |
|
|
if (!tryTerminate(false)) { |
1206 |
|
|
if (ex != null) // possibly replace if died abnormally |
1207 |
|
|
signalWork(); |
1208 |
|
|
else |
1209 |
|
|
tryReleaseWaiter(); |
1210 |
dl |
1.53 |
} |
1211 |
dl |
1.59 |
} |
1212 |
dl |
1.54 |
|
1213 |
dl |
1.91 |
// Shutdown and termination |
1214 |
|
|
|
1215 |
dl |
1.54 |
/** |
1216 |
dl |
1.53 |
* Possibly initiates and/or completes termination. |
1217 |
|
|
* |
1218 |
|
|
* @param now if true, unconditionally terminate, else only |
1219 |
|
|
* if shutdown and empty queue and no active workers |
1220 |
|
|
* @return true if now terminating or terminated |
1221 |
dl |
1.1 |
*/ |
1222 |
dl |
1.53 |
private boolean tryTerminate(boolean now) { |
1223 |
dl |
1.91 |
long c; |
1224 |
|
|
while (((c = ctl) & STOP_BIT) == 0) { |
1225 |
|
|
if (!now) { |
1226 |
|
|
if ((int)(c >> AC_SHIFT) != -parallelism) |
1227 |
|
|
return false; |
1228 |
|
|
if (!shutdown || blockedCount != 0 || quiescerCount != 0 || |
1229 |
dl |
1.95 |
queueBase != queueTop) { |
1230 |
dl |
1.91 |
if (ctl == c) // staleness check |
1231 |
|
|
return false; |
1232 |
|
|
continue; |
1233 |
|
|
} |
1234 |
|
|
} |
1235 |
|
|
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, c | STOP_BIT)) |
1236 |
|
|
startTerminating(); |
1237 |
|
|
} |
1238 |
dl |
1.95 |
if ((short)(c >>> TC_SHIFT) == -parallelism) { // signal when 0 workers |
1239 |
|
|
final ReentrantLock lock = this.submissionLock; |
1240 |
|
|
lock.lock(); |
1241 |
|
|
try { |
1242 |
|
|
termination.signalAll(); |
1243 |
|
|
} finally { |
1244 |
|
|
lock.unlock(); |
1245 |
|
|
} |
1246 |
dl |
1.53 |
} |
1247 |
dl |
1.4 |
return true; |
1248 |
dl |
1.1 |
} |
1249 |
|
|
|
1250 |
|
|
/** |
1251 |
dl |
1.91 |
* Runs up to three passes through workers: (0) Setting |
1252 |
dl |
1.95 |
* termination status for each worker, followed by wakeups up to |
1253 |
|
|
* queued workers; (1) helping cancel tasks; (2) interrupting |
1254 |
dl |
1.91 |
* lagging threads (likely in external tasks, but possibly also |
1255 |
|
|
* blocked in joins). Each pass repeats previous steps because of |
1256 |
|
|
* potential lagging thread creation. |
1257 |
dl |
1.53 |
*/ |
1258 |
|
|
private void startTerminating() { |
1259 |
dl |
1.61 |
cancelSubmissions(); |
1260 |
dl |
1.91 |
for (int pass = 0; pass < 3; ++pass) { |
1261 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1262 |
|
|
if (ws != null) { |
1263 |
|
|
for (ForkJoinWorkerThread w : ws) { |
1264 |
|
|
if (w != null) { |
1265 |
|
|
w.terminate = true; |
1266 |
|
|
if (pass > 0) { |
1267 |
|
|
w.cancelTasks(); |
1268 |
|
|
if (pass > 1 && !w.isInterrupted()) { |
1269 |
|
|
try { |
1270 |
|
|
w.interrupt(); |
1271 |
|
|
} catch (SecurityException ignore) { |
1272 |
|
|
} |
1273 |
dl |
1.61 |
} |
1274 |
|
|
} |
1275 |
|
|
} |
1276 |
|
|
} |
1277 |
dl |
1.91 |
terminateWaiters(); |
1278 |
dl |
1.61 |
} |
1279 |
dl |
1.56 |
} |
1280 |
|
|
} |
1281 |
|
|
|
1282 |
|
|
/** |
1283 |
dl |
1.91 |
* Polls and cancels all submissions. Called only during termination. |
1284 |
dl |
1.56 |
*/ |
1285 |
|
|
private void cancelSubmissions() { |
1286 |
dl |
1.91 |
while (queueBase != queueTop) { |
1287 |
|
|
ForkJoinTask<?> task = pollSubmission(); |
1288 |
|
|
if (task != null) { |
1289 |
|
|
try { |
1290 |
|
|
task.cancel(false); |
1291 |
|
|
} catch (Throwable ignore) { |
1292 |
|
|
} |
1293 |
|
|
} |
1294 |
|
|
} |
1295 |
|
|
} |
1296 |
|
|
|
1297 |
|
|
/** |
1298 |
|
|
* Tries to set the termination status of waiting workers, and |
1299 |
dl |
1.95 |
* then wakes them up (after which they will terminate). |
1300 |
dl |
1.91 |
*/ |
1301 |
|
|
private void terminateWaiters() { |
1302 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1303 |
|
|
if (ws != null) { |
1304 |
|
|
ForkJoinWorkerThread w; long c; int i, e; |
1305 |
|
|
int n = ws.length; |
1306 |
|
|
while ((i = ~(e = (int)(c = ctl)) & SMASK) < n && |
1307 |
|
|
(w = ws[i]) != null && w.eventCount == (e & E_MASK)) { |
1308 |
|
|
if (UNSAFE.compareAndSwapLong(this, ctlOffset, c, |
1309 |
|
|
(long)(w.nextWait & E_MASK) | |
1310 |
|
|
((c + AC_UNIT) & AC_MASK) | |
1311 |
|
|
(c & (TC_MASK|STOP_BIT)))) { |
1312 |
|
|
w.terminate = true; |
1313 |
|
|
w.eventCount = e + EC_UNIT; |
1314 |
|
|
if (w.parked) |
1315 |
|
|
UNSAFE.unpark(w); |
1316 |
|
|
} |
1317 |
dl |
1.53 |
} |
1318 |
|
|
} |
1319 |
dl |
1.56 |
} |
1320 |
|
|
|
1321 |
dl |
1.91 |
// misc ForkJoinWorkerThread support |
1322 |
dl |
1.53 |
|
1323 |
|
|
/** |
1324 |
dl |
1.91 |
* Increment or decrement quiescerCount. Needed only to prevent |
1325 |
|
|
* triggering shutdown if a worker is transiently inactive while |
1326 |
|
|
* checking quiescence. |
1327 |
|
|
* |
1328 |
|
|
* @param delta 1 for increment, -1 for decrement |
1329 |
dl |
1.1 |
*/ |
1330 |
dl |
1.91 |
final void addQuiescerCount(int delta) { |
1331 |
|
|
int c; |
1332 |
jsr166 |
1.102 |
do {} while (!UNSAFE.compareAndSwapInt(this, quiescerCountOffset, |
1333 |
|
|
c = quiescerCount, c + delta)); |
1334 |
dl |
1.1 |
} |
1335 |
|
|
|
1336 |
|
|
/** |
1337 |
dl |
1.91 |
* Directly increment or decrement active count without |
1338 |
|
|
* queuing. This method is used to transiently assert inactivation |
1339 |
|
|
* while checking quiescence. |
1340 |
dl |
1.61 |
* |
1341 |
dl |
1.91 |
* @param delta 1 for increment, -1 for decrement |
1342 |
dl |
1.1 |
*/ |
1343 |
dl |
1.91 |
final void addActiveCount(int delta) { |
1344 |
|
|
long d = delta < 0 ? -AC_UNIT : AC_UNIT; |
1345 |
|
|
long c; |
1346 |
|
|
do {} while (!UNSAFE.compareAndSwapLong(this, ctlOffset, c = ctl, |
1347 |
|
|
((c + d) & AC_MASK) | |
1348 |
|
|
(c & ~AC_MASK))); |
1349 |
dl |
1.1 |
} |
1350 |
|
|
|
1351 |
|
|
/** |
1352 |
dl |
1.53 |
* Returns the approximate (non-atomic) number of idle threads per |
1353 |
|
|
* active thread. |
1354 |
|
|
*/ |
1355 |
|
|
final int idlePerActive() { |
1356 |
dl |
1.91 |
// Approximate at powers of two for small values, saturate past 4 |
1357 |
|
|
int p = parallelism; |
1358 |
jsr166 |
1.102 |
int a = p + (int)(ctl >> AC_SHIFT); |
1359 |
|
|
return (a > (p >>>= 1) ? 0 : |
1360 |
|
|
a > (p >>>= 1) ? 1 : |
1361 |
|
|
a > (p >>>= 1) ? 2 : |
1362 |
|
|
a > (p >>>= 1) ? 4 : |
1363 |
|
|
8); |
1364 |
dl |
1.53 |
} |
1365 |
|
|
|
1366 |
dl |
1.91 |
// Exported methods |
1367 |
dl |
1.1 |
|
1368 |
|
|
// Constructors |
1369 |
|
|
|
1370 |
|
|
/** |
1371 |
dl |
1.42 |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1372 |
dl |
1.57 |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
1373 |
|
|
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1374 |
|
|
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1375 |
jsr166 |
1.17 |
* |
1376 |
dl |
1.1 |
* @throws SecurityException if a security manager exists and |
1377 |
|
|
* the caller is not permitted to modify threads |
1378 |
|
|
* because it does not hold {@link |
1379 |
jsr166 |
1.17 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1380 |
dl |
1.1 |
*/ |
1381 |
|
|
public ForkJoinPool() { |
1382 |
|
|
this(Runtime.getRuntime().availableProcessors(), |
1383 |
dl |
1.57 |
defaultForkJoinWorkerThreadFactory, null, false); |
1384 |
dl |
1.1 |
} |
1385 |
|
|
|
1386 |
|
|
/** |
1387 |
dl |
1.42 |
* Creates a {@code ForkJoinPool} with the indicated parallelism |
1388 |
dl |
1.57 |
* level, the {@linkplain |
1389 |
|
|
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1390 |
|
|
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1391 |
jsr166 |
1.17 |
* |
1392 |
dl |
1.42 |
* @param parallelism the parallelism level |
1393 |
dl |
1.1 |
* @throws IllegalArgumentException if parallelism less than or |
1394 |
jsr166 |
1.47 |
* equal to zero, or greater than implementation limit |
1395 |
dl |
1.1 |
* @throws SecurityException if a security manager exists and |
1396 |
|
|
* the caller is not permitted to modify threads |
1397 |
|
|
* because it does not hold {@link |
1398 |
jsr166 |
1.17 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1399 |
dl |
1.1 |
*/ |
1400 |
|
|
public ForkJoinPool(int parallelism) { |
1401 |
dl |
1.57 |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
1402 |
dl |
1.1 |
} |
1403 |
|
|
|
1404 |
|
|
/** |
1405 |
dl |
1.57 |
* Creates a {@code ForkJoinPool} with the given parameters. |
1406 |
jsr166 |
1.17 |
* |
1407 |
dl |
1.57 |
* @param parallelism the parallelism level. For default value, |
1408 |
|
|
* use {@link java.lang.Runtime#availableProcessors}. |
1409 |
|
|
* @param factory the factory for creating new threads. For default value, |
1410 |
|
|
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1411 |
dl |
1.59 |
* @param handler the handler for internal worker threads that |
1412 |
|
|
* terminate due to unrecoverable errors encountered while executing |
1413 |
jsr166 |
1.73 |
* tasks. For default value, use {@code null}. |
1414 |
dl |
1.59 |
* @param asyncMode if true, |
1415 |
dl |
1.57 |
* establishes local first-in-first-out scheduling mode for forked |
1416 |
|
|
* tasks that are never joined. This mode may be more appropriate |
1417 |
|
|
* than default locally stack-based mode in applications in which |
1418 |
|
|
* worker threads only process event-style asynchronous tasks. |
1419 |
jsr166 |
1.73 |
* For default value, use {@code false}. |
1420 |
dl |
1.1 |
* @throws IllegalArgumentException if parallelism less than or |
1421 |
jsr166 |
1.47 |
* equal to zero, or greater than implementation limit |
1422 |
jsr166 |
1.48 |
* @throws NullPointerException if the factory is null |
1423 |
dl |
1.1 |
* @throws SecurityException if a security manager exists and |
1424 |
|
|
* the caller is not permitted to modify threads |
1425 |
|
|
* because it does not hold {@link |
1426 |
jsr166 |
1.17 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1427 |
dl |
1.1 |
*/ |
1428 |
dl |
1.59 |
public ForkJoinPool(int parallelism, |
1429 |
dl |
1.57 |
ForkJoinWorkerThreadFactory factory, |
1430 |
|
|
Thread.UncaughtExceptionHandler handler, |
1431 |
|
|
boolean asyncMode) { |
1432 |
dl |
1.53 |
checkPermission(); |
1433 |
|
|
if (factory == null) |
1434 |
|
|
throw new NullPointerException(); |
1435 |
dl |
1.91 |
if (parallelism <= 0 || parallelism > MAX_ID) |
1436 |
dl |
1.1 |
throw new IllegalArgumentException(); |
1437 |
dl |
1.53 |
this.parallelism = parallelism; |
1438 |
dl |
1.1 |
this.factory = factory; |
1439 |
dl |
1.57 |
this.ueh = handler; |
1440 |
|
|
this.locallyFifo = asyncMode; |
1441 |
dl |
1.91 |
long np = (long)(-parallelism); // offset ctl counts |
1442 |
|
|
this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK); |
1443 |
|
|
this.submissionQueue = new ForkJoinTask<?>[INITIAL_QUEUE_CAPACITY]; |
1444 |
|
|
// initialize workers array with room for 2*parallelism if possible |
1445 |
|
|
int n = parallelism << 1; |
1446 |
|
|
if (n >= MAX_ID) |
1447 |
|
|
n = MAX_ID; |
1448 |
|
|
else { // See Hackers Delight, sec 3.2, where n < (1 << 16) |
1449 |
|
|
n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; |
1450 |
|
|
} |
1451 |
|
|
workers = new ForkJoinWorkerThread[n + 1]; |
1452 |
|
|
this.submissionLock = new ReentrantLock(); |
1453 |
|
|
this.termination = submissionLock.newCondition(); |
1454 |
|
|
StringBuilder sb = new StringBuilder("ForkJoinPool-"); |
1455 |
|
|
sb.append(poolNumberGenerator.incrementAndGet()); |
1456 |
|
|
sb.append("-worker-"); |
1457 |
|
|
this.workerNamePrefix = sb.toString(); |
1458 |
dl |
1.1 |
} |
1459 |
|
|
|
1460 |
|
|
// Execution methods |
1461 |
|
|
|
1462 |
|
|
/** |
1463 |
jsr166 |
1.17 |
* Performs the given task, returning its result upon completion. |
1464 |
dl |
1.91 |
* If the computation encounters an unchecked Exception or Error, |
1465 |
|
|
* it is rethrown as the outcome of this invocation. Rethrown |
1466 |
|
|
* exceptions behave in the same way as regular exceptions, but, |
1467 |
|
|
* when possible, contain stack traces (as displayed for example |
1468 |
|
|
* using {@code ex.printStackTrace()}) of both the current thread |
1469 |
|
|
* as well as the thread actually encountering the exception; |
1470 |
|
|
* minimally only the latter. |
1471 |
jsr166 |
1.17 |
* |
1472 |
dl |
1.1 |
* @param task the task |
1473 |
|
|
* @return the task's result |
1474 |
jsr166 |
1.48 |
* @throws NullPointerException if the task is null |
1475 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1476 |
|
|
* scheduled for execution |
1477 |
dl |
1.1 |
*/ |
1478 |
|
|
public <T> T invoke(ForkJoinTask<T> task) { |
1479 |
dl |
1.91 |
Thread t = Thread.currentThread(); |
1480 |
dl |
1.82 |
if (task == null) |
1481 |
|
|
throw new NullPointerException(); |
1482 |
dl |
1.91 |
if (shutdown) |
1483 |
dl |
1.82 |
throw new RejectedExecutionException(); |
1484 |
|
|
if ((t instanceof ForkJoinWorkerThread) && |
1485 |
|
|
((ForkJoinWorkerThread)t).pool == this) |
1486 |
|
|
return task.invoke(); // bypass submit if in same pool |
1487 |
|
|
else { |
1488 |
dl |
1.91 |
addSubmission(task); |
1489 |
dl |
1.82 |
return task.join(); |
1490 |
|
|
} |
1491 |
|
|
} |
1492 |
|
|
|
1493 |
|
|
/** |
1494 |
|
|
* Unless terminating, forks task if within an ongoing FJ |
1495 |
|
|
* computation in the current pool, else submits as external task. |
1496 |
|
|
*/ |
1497 |
|
|
private <T> void forkOrSubmit(ForkJoinTask<T> task) { |
1498 |
dl |
1.91 |
ForkJoinWorkerThread w; |
1499 |
|
|
Thread t = Thread.currentThread(); |
1500 |
|
|
if (shutdown) |
1501 |
dl |
1.82 |
throw new RejectedExecutionException(); |
1502 |
|
|
if ((t instanceof ForkJoinWorkerThread) && |
1503 |
dl |
1.91 |
(w = (ForkJoinWorkerThread)t).pool == this) |
1504 |
|
|
w.pushTask(task); |
1505 |
dl |
1.82 |
else |
1506 |
dl |
1.91 |
addSubmission(task); |
1507 |
dl |
1.1 |
} |
1508 |
|
|
|
1509 |
|
|
/** |
1510 |
|
|
* Arranges for (asynchronous) execution of the given task. |
1511 |
jsr166 |
1.17 |
* |
1512 |
dl |
1.1 |
* @param task the task |
1513 |
jsr166 |
1.48 |
* @throws NullPointerException if the task is null |
1514 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1515 |
|
|
* scheduled for execution |
1516 |
dl |
1.1 |
*/ |
1517 |
dl |
1.37 |
public void execute(ForkJoinTask<?> task) { |
1518 |
dl |
1.82 |
if (task == null) |
1519 |
|
|
throw new NullPointerException(); |
1520 |
|
|
forkOrSubmit(task); |
1521 |
dl |
1.1 |
} |
1522 |
|
|
|
1523 |
|
|
// AbstractExecutorService methods |
1524 |
|
|
|
1525 |
jsr166 |
1.48 |
/** |
1526 |
|
|
* @throws NullPointerException if the task is null |
1527 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1528 |
|
|
* scheduled for execution |
1529 |
|
|
*/ |
1530 |
dl |
1.1 |
public void execute(Runnable task) { |
1531 |
dl |
1.82 |
if (task == null) |
1532 |
|
|
throw new NullPointerException(); |
1533 |
dl |
1.23 |
ForkJoinTask<?> job; |
1534 |
jsr166 |
1.26 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1535 |
|
|
job = (ForkJoinTask<?>) task; |
1536 |
dl |
1.23 |
else |
1537 |
dl |
1.33 |
job = ForkJoinTask.adapt(task, null); |
1538 |
dl |
1.82 |
forkOrSubmit(job); |
1539 |
dl |
1.1 |
} |
1540 |
|
|
|
1541 |
jsr166 |
1.48 |
/** |
1542 |
dl |
1.57 |
* Submits a ForkJoinTask for execution. |
1543 |
|
|
* |
1544 |
|
|
* @param task the task to submit |
1545 |
|
|
* @return the task |
1546 |
|
|
* @throws NullPointerException if the task is null |
1547 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1548 |
|
|
* scheduled for execution |
1549 |
|
|
*/ |
1550 |
|
|
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1551 |
dl |
1.82 |
if (task == null) |
1552 |
|
|
throw new NullPointerException(); |
1553 |
|
|
forkOrSubmit(task); |
1554 |
dl |
1.57 |
return task; |
1555 |
|
|
} |
1556 |
|
|
|
1557 |
|
|
/** |
1558 |
jsr166 |
1.48 |
* @throws NullPointerException if the task is null |
1559 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1560 |
|
|
* scheduled for execution |
1561 |
|
|
*/ |
1562 |
dl |
1.1 |
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
1563 |
dl |
1.82 |
if (task == null) |
1564 |
|
|
throw new NullPointerException(); |
1565 |
dl |
1.33 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
1566 |
dl |
1.82 |
forkOrSubmit(job); |
1567 |
dl |
1.1 |
return job; |
1568 |
|
|
} |
1569 |
|
|
|
1570 |
jsr166 |
1.48 |
/** |
1571 |
|
|
* @throws NullPointerException if the task is null |
1572 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1573 |
|
|
* scheduled for execution |
1574 |
|
|
*/ |
1575 |
dl |
1.1 |
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
1576 |
dl |
1.82 |
if (task == null) |
1577 |
|
|
throw new NullPointerException(); |
1578 |
dl |
1.33 |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
1579 |
dl |
1.82 |
forkOrSubmit(job); |
1580 |
dl |
1.1 |
return job; |
1581 |
|
|
} |
1582 |
|
|
|
1583 |
jsr166 |
1.48 |
/** |
1584 |
|
|
* @throws NullPointerException if the task is null |
1585 |
|
|
* @throws RejectedExecutionException if the task cannot be |
1586 |
|
|
* scheduled for execution |
1587 |
|
|
*/ |
1588 |
dl |
1.1 |
public ForkJoinTask<?> submit(Runnable task) { |
1589 |
dl |
1.82 |
if (task == null) |
1590 |
|
|
throw new NullPointerException(); |
1591 |
dl |
1.23 |
ForkJoinTask<?> job; |
1592 |
jsr166 |
1.26 |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1593 |
|
|
job = (ForkJoinTask<?>) task; |
1594 |
dl |
1.23 |
else |
1595 |
dl |
1.33 |
job = ForkJoinTask.adapt(task, null); |
1596 |
dl |
1.82 |
forkOrSubmit(job); |
1597 |
dl |
1.1 |
return job; |
1598 |
|
|
} |
1599 |
|
|
|
1600 |
|
|
/** |
1601 |
jsr166 |
1.48 |
* @throws NullPointerException {@inheritDoc} |
1602 |
|
|
* @throws RejectedExecutionException {@inheritDoc} |
1603 |
|
|
*/ |
1604 |
dl |
1.1 |
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
1605 |
jsr166 |
1.20 |
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
1606 |
dl |
1.1 |
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
1607 |
jsr166 |
1.20 |
for (Callable<T> task : tasks) |
1608 |
dl |
1.33 |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
1609 |
jsr166 |
1.20 |
invoke(new InvokeAll<T>(forkJoinTasks)); |
1610 |
|
|
|
1611 |
|
|
@SuppressWarnings({"unchecked", "rawtypes"}) |
1612 |
dl |
1.54 |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
1613 |
jsr166 |
1.20 |
return futures; |
1614 |
dl |
1.1 |
} |
1615 |
|
|
|
1616 |
|
|
static final class InvokeAll<T> extends RecursiveAction { |
1617 |
|
|
final ArrayList<ForkJoinTask<T>> tasks; |
1618 |
|
|
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
1619 |
|
|
public void compute() { |
1620 |
jsr166 |
1.17 |
try { invokeAll(tasks); } |
1621 |
|
|
catch (Exception ignore) {} |
1622 |
dl |
1.1 |
} |
1623 |
jsr166 |
1.18 |
private static final long serialVersionUID = -7914297376763021607L; |
1624 |
dl |
1.1 |
} |
1625 |
|
|
|
1626 |
|
|
/** |
1627 |
jsr166 |
1.17 |
* Returns the factory used for constructing new workers. |
1628 |
dl |
1.1 |
* |
1629 |
|
|
* @return the factory used for constructing new workers |
1630 |
|
|
*/ |
1631 |
|
|
public ForkJoinWorkerThreadFactory getFactory() { |
1632 |
|
|
return factory; |
1633 |
|
|
} |
1634 |
|
|
|
1635 |
|
|
/** |
1636 |
dl |
1.2 |
* Returns the handler for internal worker threads that terminate |
1637 |
|
|
* due to unrecoverable errors encountered while executing tasks. |
1638 |
jsr166 |
1.17 |
* |
1639 |
jsr166 |
1.28 |
* @return the handler, or {@code null} if none |
1640 |
dl |
1.2 |
*/ |
1641 |
|
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
1642 |
dl |
1.53 |
return ueh; |
1643 |
dl |
1.2 |
} |
1644 |
|
|
|
1645 |
|
|
/** |
1646 |
dl |
1.42 |
* Returns the targeted parallelism level of this pool. |
1647 |
dl |
1.1 |
* |
1648 |
dl |
1.42 |
* @return the targeted parallelism level of this pool |
1649 |
dl |
1.1 |
*/ |
1650 |
|
|
public int getParallelism() { |
1651 |
|
|
return parallelism; |
1652 |
|
|
} |
1653 |
|
|
|
1654 |
|
|
/** |
1655 |
|
|
* Returns the number of worker threads that have started but not |
1656 |
jsr166 |
1.76 |
* yet terminated. The result returned by this method may differ |
1657 |
jsr166 |
1.29 |
* from {@link #getParallelism} when threads are created to |
1658 |
dl |
1.1 |
* maintain parallelism when others are cooperatively blocked. |
1659 |
|
|
* |
1660 |
|
|
* @return the number of worker threads |
1661 |
|
|
*/ |
1662 |
|
|
public int getPoolSize() { |
1663 |
dl |
1.91 |
return parallelism + (short)(ctl >>> TC_SHIFT); |
1664 |
dl |
1.1 |
} |
1665 |
|
|
|
1666 |
|
|
/** |
1667 |
jsr166 |
1.28 |
* Returns {@code true} if this pool uses local first-in-first-out |
1668 |
jsr166 |
1.16 |
* scheduling mode for forked tasks that are never joined. |
1669 |
dl |
1.6 |
* |
1670 |
jsr166 |
1.28 |
* @return {@code true} if this pool uses async mode |
1671 |
dl |
1.6 |
*/ |
1672 |
|
|
public boolean getAsyncMode() { |
1673 |
|
|
return locallyFifo; |
1674 |
|
|
} |
1675 |
|
|
|
1676 |
|
|
/** |
1677 |
dl |
1.2 |
* Returns an estimate of the number of worker threads that are |
1678 |
|
|
* not blocked waiting to join tasks or for other managed |
1679 |
dl |
1.53 |
* synchronization. This method may overestimate the |
1680 |
|
|
* number of running threads. |
1681 |
dl |
1.1 |
* |
1682 |
|
|
* @return the number of worker threads |
1683 |
|
|
*/ |
1684 |
|
|
public int getRunningThreadCount() { |
1685 |
dl |
1.91 |
int r = parallelism + (int)(ctl >> AC_SHIFT); |
1686 |
jsr166 |
1.102 |
return (r <= 0) ? 0 : r; // suppress momentarily negative values |
1687 |
dl |
1.1 |
} |
1688 |
|
|
|
1689 |
|
|
/** |
1690 |
dl |
1.2 |
* Returns an estimate of the number of threads that are currently |
1691 |
dl |
1.1 |
* stealing or executing tasks. This method may overestimate the |
1692 |
|
|
* number of active threads. |
1693 |
jsr166 |
1.17 |
* |
1694 |
jsr166 |
1.16 |
* @return the number of active threads |
1695 |
dl |
1.1 |
*/ |
1696 |
|
|
public int getActiveThreadCount() { |
1697 |
dl |
1.91 |
int r = parallelism + (int)(ctl >> AC_SHIFT) + blockedCount; |
1698 |
jsr166 |
1.102 |
return (r <= 0) ? 0 : r; // suppress momentarily negative values |
1699 |
dl |
1.1 |
} |
1700 |
|
|
|
1701 |
|
|
/** |
1702 |
jsr166 |
1.28 |
* Returns {@code true} if all worker threads are currently idle. |
1703 |
|
|
* An idle worker is one that cannot obtain a task to execute |
1704 |
|
|
* because none are available to steal from other threads, and |
1705 |
|
|
* there are no pending submissions to the pool. This method is |
1706 |
|
|
* conservative; it might not return {@code true} immediately upon |
1707 |
|
|
* idleness of all threads, but will eventually become true if |
1708 |
|
|
* threads remain inactive. |
1709 |
jsr166 |
1.17 |
* |
1710 |
jsr166 |
1.28 |
* @return {@code true} if all threads are currently idle |
1711 |
dl |
1.1 |
*/ |
1712 |
|
|
public boolean isQuiescent() { |
1713 |
dl |
1.91 |
return parallelism + (int)(ctl >> AC_SHIFT) + blockedCount == 0; |
1714 |
dl |
1.1 |
} |
1715 |
|
|
|
1716 |
|
|
/** |
1717 |
|
|
* Returns an estimate of the total number of tasks stolen from |
1718 |
|
|
* one thread's work queue by another. The reported value |
1719 |
|
|
* underestimates the actual total number of steals when the pool |
1720 |
|
|
* is not quiescent. This value may be useful for monitoring and |
1721 |
jsr166 |
1.17 |
* tuning fork/join programs: in general, steal counts should be |
1722 |
dl |
1.1 |
* high enough to keep threads busy, but low enough to avoid |
1723 |
|
|
* overhead and contention across threads. |
1724 |
jsr166 |
1.17 |
* |
1725 |
jsr166 |
1.16 |
* @return the number of steals |
1726 |
dl |
1.1 |
*/ |
1727 |
|
|
public long getStealCount() { |
1728 |
dl |
1.53 |
return stealCount; |
1729 |
dl |
1.1 |
} |
1730 |
|
|
|
1731 |
|
|
/** |
1732 |
dl |
1.2 |
* Returns an estimate of the total number of tasks currently held |
1733 |
|
|
* in queues by worker threads (but not including tasks submitted |
1734 |
|
|
* to the pool that have not begun executing). This value is only |
1735 |
|
|
* an approximation, obtained by iterating across all threads in |
1736 |
|
|
* the pool. This method may be useful for tuning task |
1737 |
|
|
* granularities. |
1738 |
jsr166 |
1.17 |
* |
1739 |
jsr166 |
1.16 |
* @return the number of queued tasks |
1740 |
dl |
1.1 |
*/ |
1741 |
|
|
public long getQueuedTaskCount() { |
1742 |
|
|
long count = 0; |
1743 |
dl |
1.91 |
ForkJoinWorkerThread[] ws; |
1744 |
|
|
if ((short)(ctl >>> TC_SHIFT) > -parallelism && |
1745 |
|
|
(ws = workers) != null) { |
1746 |
|
|
for (ForkJoinWorkerThread w : ws) |
1747 |
|
|
if (w != null) |
1748 |
|
|
count -= w.queueBase - w.queueTop; // must read base first |
1749 |
|
|
} |
1750 |
dl |
1.1 |
return count; |
1751 |
|
|
} |
1752 |
|
|
|
1753 |
|
|
/** |
1754 |
jsr166 |
1.40 |
* Returns an estimate of the number of tasks submitted to this |
1755 |
dl |
1.94 |
* pool that have not yet begun executing. This method may take |
1756 |
dl |
1.91 |
* time proportional to the number of submissions. |
1757 |
jsr166 |
1.17 |
* |
1758 |
jsr166 |
1.16 |
* @return the number of queued submissions |
1759 |
dl |
1.1 |
*/ |
1760 |
|
|
public int getQueuedSubmissionCount() { |
1761 |
dl |
1.91 |
return -queueBase + queueTop; |
1762 |
dl |
1.1 |
} |
1763 |
|
|
|
1764 |
|
|
/** |
1765 |
jsr166 |
1.28 |
* Returns {@code true} if there are any tasks submitted to this |
1766 |
|
|
* pool that have not yet begun executing. |
1767 |
jsr166 |
1.17 |
* |
1768 |
jsr166 |
1.16 |
* @return {@code true} if there are any queued submissions |
1769 |
dl |
1.1 |
*/ |
1770 |
|
|
public boolean hasQueuedSubmissions() { |
1771 |
dl |
1.91 |
return queueBase != queueTop; |
1772 |
dl |
1.1 |
} |
1773 |
|
|
|
1774 |
|
|
/** |
1775 |
|
|
* Removes and returns the next unexecuted submission if one is |
1776 |
|
|
* available. This method may be useful in extensions to this |
1777 |
|
|
* class that re-assign work in systems with multiple pools. |
1778 |
jsr166 |
1.17 |
* |
1779 |
jsr166 |
1.28 |
* @return the next submission, or {@code null} if none |
1780 |
dl |
1.1 |
*/ |
1781 |
|
|
protected ForkJoinTask<?> pollSubmission() { |
1782 |
dl |
1.91 |
ForkJoinTask<?> t; ForkJoinTask<?>[] q; int b, i; |
1783 |
|
|
while ((b = queueBase) != queueTop && |
1784 |
|
|
(q = submissionQueue) != null && |
1785 |
|
|
(i = (q.length - 1) & b) >= 0) { |
1786 |
|
|
long u = (i << ASHIFT) + ABASE; |
1787 |
|
|
if ((t = q[i]) != null && |
1788 |
|
|
queueBase == b && |
1789 |
|
|
UNSAFE.compareAndSwapObject(q, u, t, null)) { |
1790 |
|
|
queueBase = b + 1; |
1791 |
|
|
return t; |
1792 |
|
|
} |
1793 |
|
|
} |
1794 |
|
|
return null; |
1795 |
dl |
1.1 |
} |
1796 |
|
|
|
1797 |
|
|
/** |
1798 |
dl |
1.6 |
* Removes all available unexecuted submitted and forked tasks |
1799 |
|
|
* from scheduling queues and adds them to the given collection, |
1800 |
|
|
* without altering their execution status. These may include |
1801 |
jsr166 |
1.41 |
* artificially generated or wrapped tasks. This method is |
1802 |
|
|
* designed to be invoked only when the pool is known to be |
1803 |
dl |
1.6 |
* quiescent. Invocations at other times may not remove all |
1804 |
|
|
* tasks. A failure encountered while attempting to add elements |
1805 |
jsr166 |
1.16 |
* to collection {@code c} may result in elements being in |
1806 |
dl |
1.6 |
* neither, either or both collections when the associated |
1807 |
|
|
* exception is thrown. The behavior of this operation is |
1808 |
|
|
* undefined if the specified collection is modified while the |
1809 |
|
|
* operation is in progress. |
1810 |
jsr166 |
1.17 |
* |
1811 |
dl |
1.6 |
* @param c the collection to transfer elements into |
1812 |
|
|
* @return the number of elements transferred |
1813 |
|
|
*/ |
1814 |
dl |
1.30 |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1815 |
dl |
1.91 |
int count = 0; |
1816 |
|
|
while (queueBase != queueTop) { |
1817 |
|
|
ForkJoinTask<?> t = pollSubmission(); |
1818 |
|
|
if (t != null) { |
1819 |
|
|
c.add(t); |
1820 |
|
|
++count; |
1821 |
|
|
} |
1822 |
|
|
} |
1823 |
|
|
ForkJoinWorkerThread[] ws; |
1824 |
|
|
if ((short)(ctl >>> TC_SHIFT) > -parallelism && |
1825 |
|
|
(ws = workers) != null) { |
1826 |
|
|
for (ForkJoinWorkerThread w : ws) |
1827 |
|
|
if (w != null) |
1828 |
|
|
count += w.drainTasksTo(c); |
1829 |
|
|
} |
1830 |
dl |
1.57 |
return count; |
1831 |
|
|
} |
1832 |
|
|
|
1833 |
|
|
/** |
1834 |
dl |
1.1 |
* Returns a string identifying this pool, as well as its state, |
1835 |
|
|
* including indications of run state, parallelism level, and |
1836 |
|
|
* worker and task counts. |
1837 |
|
|
* |
1838 |
|
|
* @return a string identifying this pool, as well as its state |
1839 |
|
|
*/ |
1840 |
|
|
public String toString() { |
1841 |
|
|
long st = getStealCount(); |
1842 |
|
|
long qt = getQueuedTaskCount(); |
1843 |
|
|
long qs = getQueuedSubmissionCount(); |
1844 |
dl |
1.53 |
int pc = parallelism; |
1845 |
dl |
1.91 |
long c = ctl; |
1846 |
|
|
int tc = pc + (short)(c >>> TC_SHIFT); |
1847 |
|
|
int rc = pc + (int)(c >> AC_SHIFT); |
1848 |
|
|
if (rc < 0) // ignore transient negative |
1849 |
|
|
rc = 0; |
1850 |
|
|
int ac = rc + blockedCount; |
1851 |
|
|
String level; |
1852 |
|
|
if ((c & STOP_BIT) != 0) |
1853 |
jsr166 |
1.102 |
level = (tc == 0) ? "Terminated" : "Terminating"; |
1854 |
dl |
1.91 |
else |
1855 |
jsr166 |
1.102 |
level = shutdown ? "Shutting down" : "Running"; |
1856 |
dl |
1.1 |
return super.toString() + |
1857 |
dl |
1.91 |
"[" + level + |
1858 |
dl |
1.53 |
", parallelism = " + pc + |
1859 |
|
|
", size = " + tc + |
1860 |
|
|
", active = " + ac + |
1861 |
|
|
", running = " + rc + |
1862 |
dl |
1.1 |
", steals = " + st + |
1863 |
|
|
", tasks = " + qt + |
1864 |
|
|
", submissions = " + qs + |
1865 |
|
|
"]"; |
1866 |
|
|
} |
1867 |
|
|
|
1868 |
|
|
/** |
1869 |
|
|
* Initiates an orderly shutdown in which previously submitted |
1870 |
|
|
* tasks are executed, but no new tasks will be accepted. |
1871 |
|
|
* Invocation has no additional effect if already shut down. |
1872 |
|
|
* Tasks that are in the process of being submitted concurrently |
1873 |
|
|
* during the course of this method may or may not be rejected. |
1874 |
jsr166 |
1.17 |
* |
1875 |
dl |
1.1 |
* @throws SecurityException if a security manager exists and |
1876 |
|
|
* the caller is not permitted to modify threads |
1877 |
|
|
* because it does not hold {@link |
1878 |
jsr166 |
1.17 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1879 |
dl |
1.1 |
*/ |
1880 |
|
|
public void shutdown() { |
1881 |
|
|
checkPermission(); |
1882 |
dl |
1.91 |
shutdown = true; |
1883 |
dl |
1.53 |
tryTerminate(false); |
1884 |
dl |
1.1 |
} |
1885 |
|
|
|
1886 |
|
|
/** |
1887 |
dl |
1.42 |
* Attempts to cancel and/or stop all tasks, and reject all |
1888 |
|
|
* subsequently submitted tasks. Tasks that are in the process of |
1889 |
|
|
* being submitted or executed concurrently during the course of |
1890 |
|
|
* this method may or may not be rejected. This method cancels |
1891 |
|
|
* both existing and unexecuted tasks, in order to permit |
1892 |
|
|
* termination in the presence of task dependencies. So the method |
1893 |
|
|
* always returns an empty list (unlike the case for some other |
1894 |
|
|
* Executors). |
1895 |
jsr166 |
1.17 |
* |
1896 |
dl |
1.1 |
* @return an empty list |
1897 |
|
|
* @throws SecurityException if a security manager exists and |
1898 |
|
|
* the caller is not permitted to modify threads |
1899 |
|
|
* because it does not hold {@link |
1900 |
jsr166 |
1.17 |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1901 |
dl |
1.1 |
*/ |
1902 |
|
|
public List<Runnable> shutdownNow() { |
1903 |
|
|
checkPermission(); |
1904 |
dl |
1.91 |
shutdown = true; |
1905 |
dl |
1.53 |
tryTerminate(true); |
1906 |
dl |
1.1 |
return Collections.emptyList(); |
1907 |
|
|
} |
1908 |
|
|
|
1909 |
|
|
/** |
1910 |
jsr166 |
1.16 |
* Returns {@code true} if all tasks have completed following shut down. |
1911 |
dl |
1.1 |
* |
1912 |
jsr166 |
1.16 |
* @return {@code true} if all tasks have completed following shut down |
1913 |
dl |
1.1 |
*/ |
1914 |
|
|
public boolean isTerminated() { |
1915 |
dl |
1.91 |
long c = ctl; |
1916 |
|
|
return ((c & STOP_BIT) != 0L && |
1917 |
|
|
(short)(c >>> TC_SHIFT) == -parallelism); |
1918 |
dl |
1.1 |
} |
1919 |
|
|
|
1920 |
|
|
/** |
1921 |
jsr166 |
1.16 |
* Returns {@code true} if the process of termination has |
1922 |
dl |
1.42 |
* commenced but not yet completed. This method may be useful for |
1923 |
|
|
* debugging. A return of {@code true} reported a sufficient |
1924 |
|
|
* period after shutdown may indicate that submitted tasks have |
1925 |
dl |
1.88 |
* ignored or suppressed interruption, or are waiting for IO, |
1926 |
|
|
* causing this executor not to properly terminate. (See the |
1927 |
|
|
* advisory notes for class {@link ForkJoinTask} stating that |
1928 |
|
|
* tasks should not normally entail blocking operations. But if |
1929 |
|
|
* they do, they must abort them on interrupt.) |
1930 |
dl |
1.1 |
* |
1931 |
dl |
1.42 |
* @return {@code true} if terminating but not yet terminated |
1932 |
dl |
1.1 |
*/ |
1933 |
|
|
public boolean isTerminating() { |
1934 |
dl |
1.91 |
long c = ctl; |
1935 |
|
|
return ((c & STOP_BIT) != 0L && |
1936 |
|
|
(short)(c >>> TC_SHIFT) != -parallelism); |
1937 |
dl |
1.1 |
} |
1938 |
|
|
|
1939 |
|
|
/** |
1940 |
dl |
1.80 |
* Returns true if terminating or terminated. Used by ForkJoinWorkerThread. |
1941 |
|
|
*/ |
1942 |
|
|
final boolean isAtLeastTerminating() { |
1943 |
dl |
1.91 |
return (ctl & STOP_BIT) != 0L; |
1944 |
dl |
1.80 |
} |
1945 |
jsr166 |
1.81 |
|
1946 |
dl |
1.80 |
/** |
1947 |
jsr166 |
1.16 |
* Returns {@code true} if this pool has been shut down. |
1948 |
dl |
1.1 |
* |
1949 |
jsr166 |
1.16 |
* @return {@code true} if this pool has been shut down |
1950 |
dl |
1.1 |
*/ |
1951 |
|
|
public boolean isShutdown() { |
1952 |
dl |
1.91 |
return shutdown; |
1953 |
dl |
1.42 |
} |
1954 |
|
|
|
1955 |
|
|
/** |
1956 |
dl |
1.1 |
* Blocks until all tasks have completed execution after a shutdown |
1957 |
|
|
* request, or the timeout occurs, or the current thread is |
1958 |
|
|
* interrupted, whichever happens first. |
1959 |
|
|
* |
1960 |
|
|
* @param timeout the maximum time to wait |
1961 |
|
|
* @param unit the time unit of the timeout argument |
1962 |
jsr166 |
1.16 |
* @return {@code true} if this executor terminated and |
1963 |
|
|
* {@code false} if the timeout elapsed before termination |
1964 |
dl |
1.1 |
* @throws InterruptedException if interrupted while waiting |
1965 |
|
|
*/ |
1966 |
|
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1967 |
|
|
throws InterruptedException { |
1968 |
dl |
1.91 |
long nanos = unit.toNanos(timeout); |
1969 |
|
|
final ReentrantLock lock = this.submissionLock; |
1970 |
|
|
lock.lock(); |
1971 |
dl |
1.57 |
try { |
1972 |
dl |
1.91 |
for (;;) { |
1973 |
|
|
if (isTerminated()) |
1974 |
|
|
return true; |
1975 |
|
|
if (nanos <= 0) |
1976 |
|
|
return false; |
1977 |
|
|
nanos = termination.awaitNanos(nanos); |
1978 |
|
|
} |
1979 |
|
|
} finally { |
1980 |
|
|
lock.unlock(); |
1981 |
dl |
1.57 |
} |
1982 |
dl |
1.1 |
} |
1983 |
|
|
|
1984 |
|
|
/** |
1985 |
|
|
* Interface for extending managed parallelism for tasks running |
1986 |
jsr166 |
1.35 |
* in {@link ForkJoinPool}s. |
1987 |
|
|
* |
1988 |
dl |
1.61 |
* <p>A {@code ManagedBlocker} provides two methods. Method |
1989 |
|
|
* {@code isReleasable} must return {@code true} if blocking is |
1990 |
|
|
* not necessary. Method {@code block} blocks the current thread |
1991 |
|
|
* if necessary (perhaps internally invoking {@code isReleasable} |
1992 |
dl |
1.93 |
* before actually blocking). These actions are performed by any |
1993 |
|
|
* thread invoking {@link ForkJoinPool#managedBlock}. The |
1994 |
|
|
* unusual methods in this API accommodate synchronizers that may, |
1995 |
|
|
* but don't usually, block for long periods. Similarly, they |
1996 |
|
|
* allow more efficient internal handling of cases in which |
1997 |
|
|
* additional workers may be, but usually are not, needed to |
1998 |
|
|
* ensure sufficient parallelism. Toward this end, |
1999 |
|
|
* implementations of method {@code isReleasable} must be amenable |
2000 |
|
|
* to repeated invocation. |
2001 |
jsr166 |
1.17 |
* |
2002 |
dl |
1.1 |
* <p>For example, here is a ManagedBlocker based on a |
2003 |
|
|
* ReentrantLock: |
2004 |
jsr166 |
1.17 |
* <pre> {@code |
2005 |
|
|
* class ManagedLocker implements ManagedBlocker { |
2006 |
|
|
* final ReentrantLock lock; |
2007 |
|
|
* boolean hasLock = false; |
2008 |
|
|
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
2009 |
|
|
* public boolean block() { |
2010 |
|
|
* if (!hasLock) |
2011 |
|
|
* lock.lock(); |
2012 |
|
|
* return true; |
2013 |
|
|
* } |
2014 |
|
|
* public boolean isReleasable() { |
2015 |
|
|
* return hasLock || (hasLock = lock.tryLock()); |
2016 |
dl |
1.1 |
* } |
2017 |
jsr166 |
1.17 |
* }}</pre> |
2018 |
dl |
1.61 |
* |
2019 |
|
|
* <p>Here is a class that possibly blocks waiting for an |
2020 |
|
|
* item on a given queue: |
2021 |
|
|
* <pre> {@code |
2022 |
|
|
* class QueueTaker<E> implements ManagedBlocker { |
2023 |
|
|
* final BlockingQueue<E> queue; |
2024 |
|
|
* volatile E item = null; |
2025 |
|
|
* QueueTaker(BlockingQueue<E> q) { this.queue = q; } |
2026 |
|
|
* public boolean block() throws InterruptedException { |
2027 |
|
|
* if (item == null) |
2028 |
dl |
1.65 |
* item = queue.take(); |
2029 |
dl |
1.61 |
* return true; |
2030 |
|
|
* } |
2031 |
|
|
* public boolean isReleasable() { |
2032 |
dl |
1.65 |
* return item != null || (item = queue.poll()) != null; |
2033 |
dl |
1.61 |
* } |
2034 |
|
|
* public E getItem() { // call after pool.managedBlock completes |
2035 |
|
|
* return item; |
2036 |
|
|
* } |
2037 |
|
|
* }}</pre> |
2038 |
dl |
1.1 |
*/ |
2039 |
|
|
public static interface ManagedBlocker { |
2040 |
|
|
/** |
2041 |
|
|
* Possibly blocks the current thread, for example waiting for |
2042 |
|
|
* a lock or condition. |
2043 |
jsr166 |
1.17 |
* |
2044 |
jsr166 |
1.28 |
* @return {@code true} if no additional blocking is necessary |
2045 |
|
|
* (i.e., if isReleasable would return true) |
2046 |
dl |
1.1 |
* @throws InterruptedException if interrupted while waiting |
2047 |
jsr166 |
1.17 |
* (the method is not required to do so, but is allowed to) |
2048 |
dl |
1.1 |
*/ |
2049 |
|
|
boolean block() throws InterruptedException; |
2050 |
|
|
|
2051 |
|
|
/** |
2052 |
jsr166 |
1.28 |
* Returns {@code true} if blocking is unnecessary. |
2053 |
dl |
1.1 |
*/ |
2054 |
|
|
boolean isReleasable(); |
2055 |
|
|
} |
2056 |
|
|
|
2057 |
|
|
/** |
2058 |
|
|
* Blocks in accord with the given blocker. If the current thread |
2059 |
jsr166 |
1.38 |
* is a {@link ForkJoinWorkerThread}, this method possibly |
2060 |
|
|
* arranges for a spare thread to be activated if necessary to |
2061 |
dl |
1.57 |
* ensure sufficient parallelism while the current thread is blocked. |
2062 |
jsr166 |
1.38 |
* |
2063 |
|
|
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
2064 |
|
|
* behaviorally equivalent to |
2065 |
jsr166 |
1.17 |
* <pre> {@code |
2066 |
|
|
* while (!blocker.isReleasable()) |
2067 |
|
|
* if (blocker.block()) |
2068 |
|
|
* return; |
2069 |
|
|
* }</pre> |
2070 |
jsr166 |
1.38 |
* |
2071 |
|
|
* If the caller is a {@code ForkJoinTask}, then the pool may |
2072 |
|
|
* first be expanded to ensure parallelism, and later adjusted. |
2073 |
dl |
1.1 |
* |
2074 |
|
|
* @param blocker the blocker |
2075 |
jsr166 |
1.16 |
* @throws InterruptedException if blocker.block did so |
2076 |
dl |
1.1 |
*/ |
2077 |
dl |
1.57 |
public static void managedBlock(ManagedBlocker blocker) |
2078 |
dl |
1.1 |
throws InterruptedException { |
2079 |
|
|
Thread t = Thread.currentThread(); |
2080 |
dl |
1.61 |
if (t instanceof ForkJoinWorkerThread) { |
2081 |
|
|
ForkJoinWorkerThread w = (ForkJoinWorkerThread) t; |
2082 |
|
|
w.pool.awaitBlocker(blocker); |
2083 |
|
|
} |
2084 |
dl |
1.57 |
else { |
2085 |
|
|
do {} while (!blocker.isReleasable() && !blocker.block()); |
2086 |
|
|
} |
2087 |
dl |
1.1 |
} |
2088 |
|
|
|
2089 |
dl |
1.33 |
// AbstractExecutorService overrides. These rely on undocumented |
2090 |
|
|
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
2091 |
|
|
// implement RunnableFuture. |
2092 |
dl |
1.2 |
|
2093 |
|
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
2094 |
jsr166 |
1.34 |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value); |
2095 |
dl |
1.2 |
} |
2096 |
|
|
|
2097 |
|
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
2098 |
jsr166 |
1.34 |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
2099 |
dl |
1.2 |
} |
2100 |
|
|
|
2101 |
jsr166 |
1.27 |
// Unsafe mechanics |
2102 |
dl |
1.91 |
private static final sun.misc.Unsafe UNSAFE; |
2103 |
|
|
private static final long ctlOffset; |
2104 |
|
|
private static final long stealCountOffset; |
2105 |
|
|
private static final long blockedCountOffset; |
2106 |
|
|
private static final long quiescerCountOffset; |
2107 |
|
|
private static final long scanGuardOffset; |
2108 |
|
|
private static final long nextWorkerNumberOffset; |
2109 |
|
|
private static final long ABASE; |
2110 |
|
|
private static final int ASHIFT; |
2111 |
|
|
|
2112 |
|
|
static { |
2113 |
|
|
poolNumberGenerator = new AtomicInteger(); |
2114 |
|
|
workerSeedGenerator = new Random(); |
2115 |
|
|
modifyThreadPermission = new RuntimePermission("modifyThread"); |
2116 |
|
|
defaultForkJoinWorkerThreadFactory = |
2117 |
|
|
new DefaultForkJoinWorkerThreadFactory(); |
2118 |
jsr166 |
1.27 |
try { |
2119 |
dl |
1.91 |
UNSAFE = getUnsafe(); |
2120 |
jsr166 |
1.103 |
Class<?> k = ForkJoinPool.class; |
2121 |
dl |
1.91 |
ctlOffset = UNSAFE.objectFieldOffset |
2122 |
|
|
(k.getDeclaredField("ctl")); |
2123 |
|
|
stealCountOffset = UNSAFE.objectFieldOffset |
2124 |
|
|
(k.getDeclaredField("stealCount")); |
2125 |
|
|
blockedCountOffset = UNSAFE.objectFieldOffset |
2126 |
|
|
(k.getDeclaredField("blockedCount")); |
2127 |
|
|
quiescerCountOffset = UNSAFE.objectFieldOffset |
2128 |
|
|
(k.getDeclaredField("quiescerCount")); |
2129 |
|
|
scanGuardOffset = UNSAFE.objectFieldOffset |
2130 |
|
|
(k.getDeclaredField("scanGuard")); |
2131 |
|
|
nextWorkerNumberOffset = UNSAFE.objectFieldOffset |
2132 |
|
|
(k.getDeclaredField("nextWorkerNumber")); |
2133 |
|
|
} catch (Exception e) { |
2134 |
|
|
throw new Error(e); |
2135 |
|
|
} |
2136 |
jsr166 |
1.105 |
Class<?> a = ForkJoinTask[].class; |
2137 |
|
|
ABASE = UNSAFE.arrayBaseOffset(a); |
2138 |
|
|
int s = UNSAFE.arrayIndexScale(a); |
2139 |
dl |
1.91 |
if ((s & (s-1)) != 0) |
2140 |
|
|
throw new Error("data type scale not a power of two"); |
2141 |
|
|
ASHIFT = 31 - Integer.numberOfLeadingZeros(s); |
2142 |
jsr166 |
1.27 |
} |
2143 |
|
|
|
2144 |
|
|
/** |
2145 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
2146 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
2147 |
|
|
* into a jdk. |
2148 |
|
|
* |
2149 |
|
|
* @return a sun.misc.Unsafe |
2150 |
|
|
*/ |
2151 |
|
|
private static sun.misc.Unsafe getUnsafe() { |
2152 |
|
|
try { |
2153 |
|
|
return sun.misc.Unsafe.getUnsafe(); |
2154 |
|
|
} catch (SecurityException se) { |
2155 |
|
|
try { |
2156 |
|
|
return java.security.AccessController.doPrivileged |
2157 |
|
|
(new java.security |
2158 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
2159 |
|
|
public sun.misc.Unsafe run() throws Exception { |
2160 |
|
|
java.lang.reflect.Field f = sun.misc |
2161 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
2162 |
|
|
f.setAccessible(true); |
2163 |
|
|
return (sun.misc.Unsafe) f.get(null); |
2164 |
|
|
}}); |
2165 |
|
|
} catch (java.security.PrivilegedActionException e) { |
2166 |
|
|
throw new RuntimeException("Could not initialize intrinsics", |
2167 |
|
|
e.getCause()); |
2168 |
|
|
} |
2169 |
|
|
} |
2170 |
|
|
} |
2171 |
dl |
1.1 |
} |