21 |
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/** |
22 |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
23 |
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* A {@code ForkJoinPool} provides the entry point for submissions |
24 |
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* from non-{@code ForkJoinTask}s, as well as management and |
24 |
> |
* from non-{@code ForkJoinTask} clients, as well as management and |
25 |
|
* monitoring operations. |
26 |
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* |
27 |
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* <p>A {@code ForkJoinPool} differs from other kinds of {@link |
30 |
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* execute subtasks created by other active tasks (eventually blocking |
31 |
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* waiting for work if none exist). This enables efficient processing |
32 |
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* when most tasks spawn other subtasks (as do most {@code |
33 |
< |
* ForkJoinTask}s). A {@code ForkJoinPool} may also be used for mixed |
34 |
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* execution of some plain {@code Runnable}- or {@code Callable}- |
35 |
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* based activities along with {@code ForkJoinTask}s. When setting |
36 |
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* {@linkplain #setAsyncMode async mode}, a {@code ForkJoinPool} may |
37 |
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* also be appropriate for use with fine-grained tasks of any form |
38 |
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* that are never joined. Otherwise, other {@code ExecutorService} |
39 |
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* implementations are typically more appropriate choices. |
33 |
> |
* ForkJoinTask}s). When setting <em>asyncMode</em> to true in |
34 |
> |
* constructors, {@code ForkJoinPool}s may also be appropriate for use |
35 |
> |
* with event-style tasks that are never joined. |
36 |
|
* |
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* <p>A {@code ForkJoinPool} is constructed with a given target |
38 |
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* parallelism level; by default, equal to the number of available |
39 |
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* processors. Unless configured otherwise via {@link |
40 |
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* #setMaintainsParallelism}, the pool attempts to maintain this |
41 |
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* number of active (or available) threads by dynamically adding, |
42 |
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* suspending, or resuming internal worker threads, even if some tasks |
43 |
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* are stalled waiting to join others. However, no such adjustments |
44 |
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* are performed in the face of blocked IO or other unmanaged |
45 |
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* synchronization. The nested {@link ManagedBlocker} interface |
50 |
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* enables extension of the kinds of synchronization accommodated. |
51 |
< |
* The target parallelism level may also be changed dynamically |
52 |
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* ({@link #setParallelism}). The total number of threads may be |
53 |
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* limited using method {@link #setMaximumPoolSize}, in which case it |
54 |
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* may become possible for the activities of a pool to stall due to |
55 |
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* the lack of available threads to process new tasks. When the pool |
56 |
< |
* is executing tasks, these and other configuration setting methods |
57 |
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* may only gradually affect actual pool sizes. It is normally best |
58 |
< |
* practice to invoke these methods only when the pool is known to be |
59 |
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* quiescent. |
39 |
> |
* processors. The pool attempts to maintain enough active (or |
40 |
> |
* available) threads by dynamically adding, suspending, or resuming |
41 |
> |
* internal worker threads, even if some tasks are stalled waiting to |
42 |
> |
* join others. However, no such adjustments are guaranteed in the |
43 |
> |
* face of blocked IO or other unmanaged synchronization. The nested |
44 |
> |
* {@link ManagedBlocker} interface enables extension of the kinds of |
45 |
> |
* synchronization accommodated. |
46 |
|
* |
47 |
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* <p>In addition to execution and lifecycle control methods, this |
48 |
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* class provides status check methods (for example |
51 |
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* {@link #toString} returns indications of pool state in a |
52 |
|
* convenient form for informal monitoring. |
53 |
|
* |
54 |
+ |
* <p> As is the case with other ExecutorServices, there are three |
55 |
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* main task execution methods summarized in the following |
56 |
+ |
* table. These are designed to be used by clients not already engaged |
57 |
+ |
* in fork/join computations in the current pool. The main forms of |
58 |
+ |
* these methods accept instances of {@code ForkJoinTask}, but |
59 |
+ |
* overloaded forms also allow mixed execution of plain {@code |
60 |
+ |
* Runnable}- or {@code Callable}- based activities as well. However, |
61 |
+ |
* tasks that are already executing in a pool should normally |
62 |
+ |
* <em>NOT</em> use these pool execution methods, but instead use the |
63 |
+ |
* within-computation forms listed in the table. |
64 |
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* |
65 |
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* <table BORDER CELLPADDING=3 CELLSPACING=1> |
66 |
+ |
* <tr> |
67 |
+ |
* <td></td> |
68 |
+ |
* <td ALIGN=CENTER> <b>Call from non-fork/join clients</b></td> |
69 |
+ |
* <td ALIGN=CENTER> <b>Call from within fork/join computations</b></td> |
70 |
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* </tr> |
71 |
+ |
* <tr> |
72 |
+ |
* <td> <b>Arange async execution</td> |
73 |
+ |
* <td> {@link #execute(ForkJoinTask)}</td> |
74 |
+ |
* <td> {@link ForkJoinTask#fork}</td> |
75 |
+ |
* </tr> |
76 |
+ |
* <tr> |
77 |
+ |
* <td> <b>Await and obtain result</td> |
78 |
+ |
* <td> {@link #invoke(ForkJoinTask)}</td> |
79 |
+ |
* <td> {@link ForkJoinTask#invoke}</td> |
80 |
+ |
* </tr> |
81 |
+ |
* <tr> |
82 |
+ |
* <td> <b>Arrange exec and obtain Future</td> |
83 |
+ |
* <td> {@link #submit(ForkJoinTask)}</td> |
84 |
+ |
* <td> {@link ForkJoinTask#fork} (ForkJoinTasks <em>are</em> Futures)</td> |
85 |
+ |
* </tr> |
86 |
+ |
* </table> |
87 |
+ |
* |
88 |
|
* <p><b>Sample Usage.</b> Normally a single {@code ForkJoinPool} is |
89 |
|
* used for all parallel task execution in a program or subsystem. |
90 |
|
* Otherwise, use would not usually outweigh the construction and |
109 |
|
* {@code IllegalArgumentException}. |
110 |
|
* |
111 |
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* <p>This implementation rejects submitted tasks (that is, by throwing |
112 |
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* {@link RejectedExecutionException}) only when the pool is shut down. |
112 |
> |
* {@link RejectedExecutionException}) only when the pool is shut down |
113 |
> |
* or internal resources have been exhuasted. |
114 |
|
* |
115 |
|
* @since 1.7 |
116 |
|
* @author Doug Lea |
137 |
|
* of tasks profit from cache affinities, but others are harmed by |
138 |
|
* cache pollution effects.) |
139 |
|
* |
140 |
+ |
* Beyond work-stealing support and essential bookkeeping, the |
141 |
+ |
* main responsibility of this framework is to take actions when |
142 |
+ |
* one worker is waiting to join a task stolen (or always held by) |
143 |
+ |
* another. Becauae we are multiplexing many tasks on to a pool |
144 |
+ |
* of workers, we can't just let them block (as in Thread.join). |
145 |
+ |
* We also cannot just reassign the joiner's run-time stack with |
146 |
+ |
* another and replace it later, which would be a form of |
147 |
+ |
* "continuation", that even if possible is not necessarily a good |
148 |
+ |
* idea. Given that the creation costs of most threads on most |
149 |
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* systems mainly surrounds setting up runtime stacks, thread |
150 |
+ |
* creation and switching is usually not much more expensive than |
151 |
+ |
* stack creation and switching, and is more flexible). Instead we |
152 |
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* combine two tactics: |
153 |
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* |
154 |
+ |
* Helping: Arranging for the joiner to execute some task that it |
155 |
+ |
* would be running if the steal had not occurred. Method |
156 |
+ |
* ForkJoinWorkerThread.helpJoinTask tracks joining->stealing |
157 |
+ |
* links to try to find such a task. |
158 |
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* |
159 |
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* Compensating: Unless there are already enough live threads, |
160 |
+ |
* creating or or re-activating a spare thread to compensate |
161 |
+ |
* for the (blocked) joiner until it unblocks. Spares then |
162 |
+ |
* suspend at their next opportunity or eventually die if |
163 |
+ |
* unused for too long. See below and the internal |
164 |
+ |
* documentation for tryAwaitJoin for more details about |
165 |
+ |
* compensation rules. |
166 |
+ |
* |
167 |
+ |
* Because the determining existence of conservatively safe |
168 |
+ |
* helping targets, the availability of already-created spares, |
169 |
+ |
* and the apparent need to create new spares are all racy and |
170 |
+ |
* require heuristic guidance, joins (in |
171 |
+ |
* ForkJoinWorkerThread.joinTask) interleave these options until |
172 |
+ |
* successful. Creating a new spare always succeeds, but also |
173 |
+ |
* increases application footprint, so we try to avoid it, within |
174 |
+ |
* reason. |
175 |
+ |
* |
176 |
+ |
* The ManagedBlocker extension API can't use helping so uses a |
177 |
+ |
* special version of compensation in method awaitBlocker. |
178 |
+ |
* |
179 |
|
* The main throughput advantages of work-stealing stem from |
180 |
|
* decentralized control -- workers mostly steal tasks from each |
181 |
|
* other. We do not want to negate this by creating bottlenecks |
182 |
< |
* implementing the management responsibilities of this class. So |
183 |
< |
* we use a collection of techniques that avoid, reduce, or cope |
184 |
< |
* well with contention. These entail several instances of |
185 |
< |
* bit-packing into CASable fields to maintain only the minimally |
186 |
< |
* required atomicity. To enable such packing, we restrict maximum |
187 |
< |
* parallelism to (1<<15)-1 (enabling twice this to fit into a 16 |
188 |
< |
* bit field), which is far in excess of normal operating range. |
189 |
< |
* Even though updates to some of these bookkeeping fields do |
190 |
< |
* sometimes contend with each other, they don't normally |
191 |
< |
* cache-contend with updates to others enough to warrant memory |
192 |
< |
* padding or isolation. So they are all held as fields of |
193 |
< |
* ForkJoinPool objects. The main capabilities are as follows: |
182 |
> |
* implementing other management responsibilities. So we use a |
183 |
> |
* collection of techniques that avoid, reduce, or cope well with |
184 |
> |
* contention. These entail several instances of bit-packing into |
185 |
> |
* CASable fields to maintain only the minimally required |
186 |
> |
* atomicity. To enable such packing, we restrict maximum |
187 |
> |
* parallelism to (1<<15)-1 (enabling twice this (to accommodate |
188 |
> |
* unbalanced increments and decrements) to fit into a 16 bit |
189 |
> |
* field, which is far in excess of normal operating range. Even |
190 |
> |
* though updates to some of these bookkeeping fields do sometimes |
191 |
> |
* contend with each other, they don't normally cache-contend with |
192 |
> |
* updates to others enough to warrant memory padding or |
193 |
> |
* isolation. So they are all held as fields of ForkJoinPool |
194 |
> |
* objects. The main capabilities are as follows: |
195 |
|
* |
196 |
|
* 1. Creating and removing workers. Workers are recorded in the |
197 |
|
* "workers" array. This is an array as opposed to some other data |
201 |
|
* (workerLock) but the array is otherwise concurrently readable, |
202 |
|
* and accessed directly by workers. To simplify index-based |
203 |
|
* operations, the array size is always a power of two, and all |
204 |
< |
* readers must tolerate null slots. Currently, all but the first |
205 |
< |
* worker thread creation is on-demand, triggered by task |
206 |
< |
* submissions, replacement of terminated workers, and/or |
207 |
< |
* compensation for blocked workers. However, all other support |
208 |
< |
* code is set up to work with other policies. |
204 |
> |
* readers must tolerate null slots. Currently, all worker thread |
205 |
> |
* creation is on-demand, triggered by task submissions, |
206 |
> |
* replacement of terminated workers, and/or compensation for |
207 |
> |
* blocked workers. However, all other support code is set up to |
208 |
> |
* work with other policies. |
209 |
|
* |
210 |
|
* 2. Bookkeeping for dynamically adding and removing workers. We |
211 |
< |
* maintain a given level of parallelism (or, if |
212 |
< |
* maintainsParallelism is false, at least avoid starvation). When |
152 |
< |
* some workers are known to be blocked (on joins or via |
211 |
> |
* aim to approximately maintain the given level of parallelism. |
212 |
> |
* When some workers are known to be blocked (on joins or via |
213 |
|
* ManagedBlocker), we may create or resume others to take their |
214 |
|
* place until they unblock (see below). Implementing this |
215 |
|
* requires counts of the number of "running" threads (i.e., those |
216 |
|
* that are neither blocked nor artifically suspended) as well as |
217 |
|
* the total number. These two values are packed into one field, |
218 |
|
* "workerCounts" because we need accurate snapshots when deciding |
219 |
< |
* to create, resume or suspend. To support these decisions, |
220 |
< |
* updates must be prospective (not retrospective). For example, |
221 |
< |
* the running count is decremented before blocking by a thread |
222 |
< |
* about to block, but incremented by the thread about to unblock |
163 |
< |
* it. (In a few cases, these prospective updates may need to be |
164 |
< |
* rolled back, for example when deciding to create a new worker |
165 |
< |
* but the thread factory fails or returns null. In these cases, |
166 |
< |
* we are no worse off wrt other decisions than we would be |
167 |
< |
* otherwise.) Updates to the workerCounts field sometimes |
168 |
< |
* transiently encounter a fair amount of contention when join |
169 |
< |
* dependencies are such that many threads block or unblock at |
170 |
< |
* about the same time. We alleviate this by sometimes bundling |
171 |
< |
* updates (for example blocking one thread on join and resuming a |
172 |
< |
* spare cancel each other out), and in most other cases |
173 |
< |
* performing an alternative action (like releasing waiters and |
174 |
< |
* finding spares; see below) as a more productive form of |
175 |
< |
* backoff. |
219 |
> |
* to create, resume or suspend. Note however that the |
220 |
> |
* correspondance of these counts to reality is not guaranteed. In |
221 |
> |
* particular updates for unblocked threads may lag until they |
222 |
> |
* actually wake up. |
223 |
|
* |
224 |
|
* 3. Maintaining global run state. The run state of the pool |
225 |
|
* consists of a runLevel (SHUTDOWN, TERMINATING, etc) similar to |
268 |
|
* that only releases idle workers until it detects interference |
269 |
|
* by other threads trying to release, and lets them take |
270 |
|
* over. The net effect is a tree-like diffusion of signals, where |
271 |
< |
* released threads and possibly others) help with unparks. To |
271 |
> |
* released threads (and possibly others) help with unparks. To |
272 |
|
* further reduce contention effects a bit, failed CASes to |
273 |
|
* increment field eventCount are tolerated without retries. |
274 |
|
* Conceptually they are merged into the same event, which is OK |
277 |
|
* 5. Managing suspension of extra workers. When a worker is about |
278 |
|
* to block waiting for a join (or via ManagedBlockers), we may |
279 |
|
* create a new thread to maintain parallelism level, or at least |
280 |
< |
* avoid starvation (see below). Usually, extra threads are needed |
281 |
< |
* for only very short periods, yet join dependencies are such |
282 |
< |
* that we sometimes need them in bursts. Rather than create new |
283 |
< |
* threads each time this happens, we suspend no-longer-needed |
284 |
< |
* extra ones as "spares". For most purposes, we don't distinguish |
285 |
< |
* "extra" spare threads from normal "core" threads: On each call |
286 |
< |
* to preStep (the only point at which we can do this) a worker |
280 |
> |
* avoid starvation. Usually, extra threads are needed for only |
281 |
> |
* very short periods, yet join dependencies are such that we |
282 |
> |
* sometimes need them in bursts. Rather than create new threads |
283 |
> |
* each time this happens, we suspend no-longer-needed extra ones |
284 |
> |
* as "spares". For most purposes, we don't distinguish "extra" |
285 |
> |
* spare threads from normal "core" threads: On each call to |
286 |
> |
* preStep (the only point at which we can do this) a worker |
287 |
|
* checks to see if there are now too many running workers, and if |
288 |
< |
* so, suspends itself. Methods preJoin and doBlock look for |
289 |
< |
* suspended threads to resume before considering creating a new |
290 |
< |
* replacement. We don't need a special data structure to maintain |
291 |
< |
* spares; simply scanning the workers array looking for |
292 |
< |
* worker.isSuspended() is fine because the calling thread is |
293 |
< |
* otherwise not doing anything useful anyway; we are at least as |
294 |
< |
* happy if after locating a spare, the caller doesn't actually |
295 |
< |
* block because the join is ready before we try to adjust and |
296 |
< |
* compensate. Note that this is intrinsically racy. One thread |
297 |
< |
* may become a spare at about the same time as another is |
298 |
< |
* needlessly being created. We counteract this and related slop |
299 |
< |
* in part by requiring resumed spares to immediately recheck (in |
300 |
< |
* preStep) to see whether they they should re-suspend. The only |
301 |
< |
* effective difference between "extra" and "core" threads is that |
302 |
< |
* we allow the "extra" ones to time out and die if they are not |
303 |
< |
* resumed within a keep-alive interval of a few seconds. This is |
304 |
< |
* implemented mainly within ForkJoinWorkerThread, but requires |
288 |
> |
* so, suspends itself. Methods tryAwaitJoin and awaitBlocker |
289 |
> |
* look for suspended threads to resume before considering |
290 |
> |
* creating a new replacement. We don't need a special data |
291 |
> |
* structure to maintain spares; simply scanning the workers array |
292 |
> |
* looking for worker.isSuspended() is fine because the calling |
293 |
> |
* thread is otherwise not doing anything useful anyway; we are at |
294 |
> |
* least as happy if after locating a spare, the caller doesn't |
295 |
> |
* actually block because the join is ready before we try to |
296 |
> |
* adjust and compensate. Note that this is intrinsically racy. |
297 |
> |
* One thread may become a spare at about the same time as another |
298 |
> |
* is needlessly being created. We counteract this and related |
299 |
> |
* slop in part by requiring resumed spares to immediately recheck |
300 |
> |
* (in preStep) to see whether they they should re-suspend. The |
301 |
> |
* only effective difference between "extra" and "core" threads is |
302 |
> |
* that we allow the "extra" ones to time out and die if they are |
303 |
> |
* not resumed within a keep-alive interval of a few seconds. This |
304 |
> |
* is implemented mainly within ForkJoinWorkerThread, but requires |
305 |
|
* some coordination (isTrimmed() -- meaning killed while |
306 |
|
* suspended) to correctly maintain pool counts. |
307 |
|
* |
308 |
|
* 6. Deciding when to create new workers. The main dynamic |
309 |
|
* control in this class is deciding when to create extra threads, |
310 |
< |
* in methods preJoin and doBlock. We always need to create one |
311 |
< |
* when the number of running threads becomes zero. But because |
312 |
< |
* blocked joins are typically dependent, we don't necessarily |
313 |
< |
* need or want one-to-one replacement. Using a one-to-one |
314 |
< |
* compensation rule often leads to enough useless overhead |
315 |
< |
* creating, suspending, resuming, and/or killing threads to |
316 |
< |
* signficantly degrade throughput. We use a rule reflecting the |
317 |
< |
* idea that, the more spare threads you already have, the more |
318 |
< |
* evidence you need to create another one; where "evidence" is |
319 |
< |
* expressed as the current deficit -- target minus running |
320 |
< |
* threads. To reduce flickering and drift around target values, |
321 |
< |
* the relation is quadratic: adding a spare if (dc*dc)>=(sc*pc) |
322 |
< |
* (where dc is deficit, sc is number of spare threads and pc is |
323 |
< |
* target parallelism.) This effectively reduces churn at the |
324 |
< |
* price of systematically undershooting target parallelism when |
325 |
< |
* many threads are blocked. However, biasing toward undeshooting |
279 |
< |
* partially compensates for the above mechanics to suspend extra |
280 |
< |
* threads, that normally lead to overshoot because we can only |
281 |
< |
* suspend workers in-between top-level actions. It also better |
282 |
< |
* copes with the fact that some of the methods in this class tend |
283 |
< |
* to never become compiled (but are interpreted), so some |
284 |
< |
* components of the entire set of controls might execute many |
285 |
< |
* times faster than others. And similarly for cases where the |
286 |
< |
* apparent lack of work is just due to GC stalls and other |
287 |
< |
* transient system activity. |
288 |
< |
* |
289 |
< |
* 7. Maintaining other configuration parameters and monitoring |
290 |
< |
* statistics. Updates to fields controlling parallelism level, |
291 |
< |
* max size, etc can only meaningfully take effect for individual |
292 |
< |
* threads upon their next top-level actions; i.e., between |
293 |
< |
* stealing/running tasks/submission, which are separated by calls |
294 |
< |
* to preStep. Memory ordering for these (assumed infrequent) |
295 |
< |
* reconfiguration calls is ensured by using reads and writes to |
296 |
< |
* volatile field workerCounts (that must be read in preStep anyway) |
297 |
< |
* as "fences" -- user-level reads are preceded by reads of |
298 |
< |
* workCounts, and writes are followed by no-op CAS to |
299 |
< |
* workerCounts. The values reported by other management and |
300 |
< |
* monitoring methods are either computed on demand, or are kept |
301 |
< |
* in fields that are only updated when threads are otherwise |
302 |
< |
* idle. |
310 |
> |
* in methods awaitJoin and awaitBlocker. We always need to create |
311 |
> |
* one when the number of running threads would become zero and |
312 |
> |
* all workers are busy. However, this is not easy to detect |
313 |
> |
* reliably in the presence of transients so we use retries and |
314 |
> |
* allow slack (in tryAwaitJoin) to reduce false alarms. These |
315 |
> |
* effectively reduce churn at the price of systematically |
316 |
> |
* undershooting target parallelism when many threads are blocked. |
317 |
> |
* However, biasing toward undeshooting partially compensates for |
318 |
> |
* the above mechanics to suspend extra threads, that normally |
319 |
> |
* lead to overshoot because we can only suspend workers |
320 |
> |
* in-between top-level actions. It also better copes with the |
321 |
> |
* fact that some of the methods in this class tend to never |
322 |
> |
* become compiled (but are interpreted), so some components of |
323 |
> |
* the entire set of controls might execute many times faster than |
324 |
> |
* others. And similarly for cases where the apparent lack of work |
325 |
> |
* is just due to GC stalls and other transient system activity. |
326 |
|
* |
327 |
|
* Beware that there is a lot of representation-level coupling |
328 |
|
* among classes ForkJoinPool, ForkJoinWorkerThread, and |
337 |
|
* "while ((local = field) != 0)") which are usually the simplest |
338 |
|
* way to ensure read orderings. Also several occurrences of the |
339 |
|
* unusual "do {} while(!cas...)" which is the simplest way to |
340 |
< |
* force an update of a CAS'ed variable. There are also a few |
341 |
< |
* other coding oddities that help some methods perform reasonably |
342 |
< |
* even when interpreted (not compiled). |
340 |
> |
* force an update of a CAS'ed variable. There are also other |
341 |
> |
* coding oddities that help some methods perform reasonably even |
342 |
> |
* when interpreted (not compiled), at the expense of messiness. |
343 |
|
* |
344 |
|
* The order of declarations in this file is: (1) statics (2) |
345 |
|
* fields (along with constants used when unpacking some of them) |
368 |
|
* Default ForkJoinWorkerThreadFactory implementation; creates a |
369 |
|
* new ForkJoinWorkerThread. |
370 |
|
*/ |
371 |
< |
static class DefaultForkJoinWorkerThreadFactory |
371 |
> |
static class DefaultForkJoinWorkerThreadFactory |
372 |
|
implements ForkJoinWorkerThreadFactory { |
373 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
374 |
|
return new ForkJoinWorkerThread(pool); |
436 |
|
/** |
437 |
|
* Latch released upon termination. |
438 |
|
*/ |
439 |
< |
private final CountDownLatch terminationLatch; |
439 |
> |
private final Phaser termination; |
440 |
|
|
441 |
|
/** |
442 |
|
* Creation factory for worker threads. |
458 |
|
private volatile long eventWaiters; |
459 |
|
|
460 |
|
private static final int EVENT_COUNT_SHIFT = 32; |
461 |
< |
private static final long WAITER_INDEX_MASK = (1L << EVENT_COUNT_SHIFT)-1L; |
461 |
> |
private static final long WAITER_ID_MASK = (1L << EVENT_COUNT_SHIFT)-1L; |
462 |
|
|
463 |
|
/** |
464 |
|
* A counter for events that may wake up worker threads: |
497 |
|
* making decisions about creating and suspending spare |
498 |
|
* threads. Updated only by CAS. Note that adding a new worker |
499 |
|
* requires incrementing both counts, since workers start off in |
500 |
< |
* running state. This field is also used for memory-fencing |
478 |
< |
* configuration parameters. |
500 |
> |
* running state. |
501 |
|
*/ |
502 |
|
private volatile int workerCounts; |
503 |
|
|
506 |
|
private static final int ONE_RUNNING = 1; |
507 |
|
private static final int ONE_TOTAL = 1 << TOTAL_COUNT_SHIFT; |
508 |
|
|
487 |
– |
/* |
488 |
– |
* Fields parallelism. maxPoolSize, locallyFifo, |
489 |
– |
* maintainsParallelism, and ueh are non-volatile, but external |
490 |
– |
* reads/writes use workerCount fences to ensure visability. |
491 |
– |
*/ |
492 |
– |
|
509 |
|
/** |
510 |
|
* The target parallelism level. |
511 |
+ |
* Accessed directly by ForkJoinWorkerThreads. |
512 |
|
*/ |
513 |
< |
private int parallelism; |
497 |
< |
|
498 |
< |
/** |
499 |
< |
* The maximum allowed pool size. |
500 |
< |
*/ |
501 |
< |
private int maxPoolSize; |
513 |
> |
final int parallelism; |
514 |
|
|
515 |
|
/** |
516 |
|
* True if use local fifo, not default lifo, for local polling |
517 |
< |
* Replicated by ForkJoinWorkerThreads |
517 |
> |
* Read by, and replicated by ForkJoinWorkerThreads |
518 |
|
*/ |
519 |
< |
private boolean locallyFifo; |
519 |
> |
final boolean locallyFifo; |
520 |
|
|
521 |
|
/** |
522 |
< |
* Controls whether to add spares to maintain parallelism |
522 |
> |
* The uncaught exception handler used when any worker abruptly |
523 |
> |
* terminates. |
524 |
|
*/ |
525 |
< |
private boolean maintainsParallelism; |
513 |
< |
|
514 |
< |
/** |
515 |
< |
* The uncaught exception handler used when any worker |
516 |
< |
* abruptly terminates |
517 |
< |
*/ |
518 |
< |
private Thread.UncaughtExceptionHandler ueh; |
525 |
> |
private final Thread.UncaughtExceptionHandler ueh; |
526 |
|
|
527 |
|
/** |
528 |
|
* Pool number, just for assigning useful names to worker threads |
529 |
|
*/ |
530 |
|
private final int poolNumber; |
531 |
|
|
532 |
< |
// utilities for updating fields |
532 |
> |
// Utilities for CASing fields. Note that several of these |
533 |
> |
// are manually inlined by callers |
534 |
|
|
535 |
|
/** |
536 |
< |
* Adds delta to running count. Used mainly by ForkJoinTask. |
529 |
< |
* |
530 |
< |
* @param delta the number to add |
536 |
> |
* Increments running count. Also used by ForkJoinTask. |
537 |
|
*/ |
538 |
< |
final void updateRunningCount(int delta) { |
539 |
< |
int wc; |
538 |
> |
final void incrementRunningCount() { |
539 |
> |
int c; |
540 |
|
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
541 |
< |
wc = workerCounts, |
542 |
< |
wc + delta)); |
541 |
> |
c = workerCounts, |
542 |
> |
c + ONE_RUNNING)); |
543 |
|
} |
544 |
|
|
545 |
|
/** |
546 |
< |
* Write fence for user modifications of pool parameters |
541 |
< |
* (parallelism. etc). Note that it doesn't matter if CAS fails. |
546 |
> |
* Tries to decrement running count unless already zero |
547 |
|
*/ |
548 |
< |
private void workerCountWriteFence() { |
549 |
< |
int wc; |
550 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
551 |
< |
wc = workerCounts, wc); |
548 |
> |
final boolean tryDecrementRunningCount() { |
549 |
> |
int wc = workerCounts; |
550 |
> |
if ((wc & RUNNING_COUNT_MASK) == 0) |
551 |
> |
return false; |
552 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
553 |
> |
wc, wc - ONE_RUNNING); |
554 |
|
} |
555 |
|
|
556 |
|
/** |
557 |
< |
* Read fence for external reads of pool parameters |
551 |
< |
* (parallelism. maxPoolSize, etc). |
557 |
> |
* Tries to increment running count |
558 |
|
*/ |
559 |
< |
private void workerCountReadFence() { |
560 |
< |
int ignore = workerCounts; |
559 |
> |
final boolean tryIncrementRunningCount() { |
560 |
> |
int wc; |
561 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
562 |
> |
wc = workerCounts, wc + ONE_RUNNING); |
563 |
|
} |
564 |
|
|
565 |
|
/** |
610 |
|
lock.lock(); |
611 |
|
try { |
612 |
|
ForkJoinWorkerThread[] ws = workers; |
613 |
< |
int len = ws.length; |
614 |
< |
if (k < 0 || k >= len || ws[k] != null) { |
615 |
< |
for (k = 0; k < len && ws[k] != null; ++k) |
613 |
> |
int nws = ws.length; |
614 |
> |
if (k < 0 || k >= nws || ws[k] != null) { |
615 |
> |
for (k = 0; k < nws && ws[k] != null; ++k) |
616 |
|
; |
617 |
< |
if (k == len) |
618 |
< |
ws = Arrays.copyOf(ws, len << 1); |
617 |
> |
if (k == nws) |
618 |
> |
ws = Arrays.copyOf(ws, nws << 1); |
619 |
|
} |
620 |
|
ws[k] = w; |
621 |
|
workers = ws; // volatile array write ensures slot visibility |
656 |
|
try { |
657 |
|
w = factory.newThread(this); |
658 |
|
} finally { // Adjust on either null or exceptional factory return |
659 |
< |
if (w == null) { |
659 |
> |
if (w == null) |
660 |
|
onWorkerCreationFailure(); |
653 |
– |
return null; |
654 |
– |
} |
661 |
|
} |
662 |
< |
w.start(recordWorker(w), locallyFifo, ueh); |
662 |
> |
if (w != null) |
663 |
> |
w.start(recordWorker(w), ueh); |
664 |
|
return w; |
665 |
|
} |
666 |
|
|
668 |
|
* Adjusts counts upon failure to create worker |
669 |
|
*/ |
670 |
|
private void onWorkerCreationFailure() { |
671 |
< |
int c; |
672 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
673 |
< |
c = workerCounts, |
674 |
< |
c - (ONE_RUNNING|ONE_TOTAL))); |
671 |
> |
for (;;) { |
672 |
> |
int wc = workerCounts; |
673 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
674 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
675 |
> |
if (rc == 0 || wc == 0) |
676 |
> |
Thread.yield(); // must wait for other counts to settle |
677 |
> |
else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
678 |
> |
wc - (ONE_RUNNING|ONE_TOTAL))) |
679 |
> |
break; |
680 |
> |
} |
681 |
|
tryTerminate(false); // in case of failure during shutdown |
682 |
|
} |
683 |
|
|
684 |
|
/** |
685 |
< |
* Create enough total workers to establish target parallelism, |
685 |
> |
* Creates enough total workers to establish target parallelism, |
686 |
|
* giving up if terminating or addWorker fails |
687 |
|
*/ |
688 |
|
private void ensureEnoughTotalWorkers() { |
689 |
|
int wc; |
690 |
< |
while (runState < TERMINATING && |
691 |
< |
((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism) { |
690 |
> |
while (((wc = workerCounts) >>> TOTAL_COUNT_SHIFT) < parallelism && |
691 |
> |
runState < TERMINATING) { |
692 |
|
if ((UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
693 |
|
wc, wc + (ONE_RUNNING|ONE_TOTAL)) && |
694 |
|
addWorker() == null)) |
711 |
|
} |
712 |
|
forgetWorker(w); |
713 |
|
|
714 |
< |
// decrement total count, and if was running, running count |
715 |
< |
int unit = w.isTrimmed()? ONE_TOTAL : (ONE_RUNNING|ONE_TOTAL); |
716 |
< |
int wc; |
717 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
718 |
< |
wc = workerCounts, wc - unit)); |
714 |
> |
// Decrement total count, and if was running, running count |
715 |
> |
// Spin (waiting for other updates) if either would be negative |
716 |
> |
int nr = w.isTrimmed() ? 0 : ONE_RUNNING; |
717 |
> |
int unit = ONE_TOTAL + nr; |
718 |
> |
for (;;) { |
719 |
> |
int wc = workerCounts; |
720 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
721 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
722 |
> |
if (rc - nr < 0 || tc == 0) |
723 |
> |
Thread.yield(); // back off if waiting for other updates |
724 |
> |
else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
725 |
> |
wc, wc - unit)) |
726 |
> |
break; |
727 |
> |
} |
728 |
|
|
729 |
|
accumulateStealCount(w); // collect final count |
730 |
|
if (!tryTerminate(false)) |
734 |
|
// Waiting for and signalling events |
735 |
|
|
736 |
|
/** |
715 |
– |
* Ensures eventCount on exit is different (mod 2^32) than on |
716 |
– |
* entry. CAS failures are OK -- any change in count suffices. |
717 |
– |
*/ |
718 |
– |
private void advanceEventCount() { |
719 |
– |
int c; |
720 |
– |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c = eventCount, c+1); |
721 |
– |
} |
722 |
– |
|
723 |
– |
/** |
737 |
|
* Releases workers blocked on a count not equal to current count. |
738 |
+ |
* @return true if any released |
739 |
|
*/ |
740 |
< |
final void releaseWaiters() { |
740 |
> |
private void releaseWaiters() { |
741 |
|
long top; |
742 |
< |
int id; |
729 |
< |
while ((id = (int)((top = eventWaiters) & WAITER_INDEX_MASK)) > 0 && |
730 |
< |
(int)(top >>> EVENT_COUNT_SHIFT) != eventCount) { |
742 |
> |
while ((top = eventWaiters) != 0L) { |
743 |
|
ForkJoinWorkerThread[] ws = workers; |
744 |
< |
ForkJoinWorkerThread w; |
745 |
< |
if (ws.length >= id && (w = ws[id - 1]) != null && |
746 |
< |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
747 |
< |
top, w.nextWaiter)) |
748 |
< |
LockSupport.unpark(w); |
744 |
> |
int n = ws.length; |
745 |
> |
for (;;) { |
746 |
> |
int i = ((int)(top & WAITER_ID_MASK)) - 1; |
747 |
> |
int e = (int)(top >>> EVENT_COUNT_SHIFT); |
748 |
> |
if (i < 0 || e == eventCount) |
749 |
> |
return; |
750 |
> |
ForkJoinWorkerThread w; |
751 |
> |
if (i < n && (w = ws[i]) != null && |
752 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
753 |
> |
top, w.nextWaiter)) { |
754 |
> |
LockSupport.unpark(w); |
755 |
> |
top = eventWaiters; |
756 |
> |
} |
757 |
> |
else |
758 |
> |
break; // possibly stale; reread |
759 |
> |
} |
760 |
|
} |
761 |
|
} |
762 |
|
|
763 |
|
/** |
764 |
+ |
* Ensures eventCount on exit is different (mod 2^32) than on |
765 |
+ |
* entry and wakes up all waiters |
766 |
+ |
*/ |
767 |
+ |
private void signalEvent() { |
768 |
+ |
int c; |
769 |
+ |
do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
770 |
+ |
c = eventCount, c+1)); |
771 |
+ |
releaseWaiters(); |
772 |
+ |
} |
773 |
+ |
|
774 |
+ |
/** |
775 |
|
* Advances eventCount and releases waiters until interference by |
776 |
|
* other releasing threads is detected. |
777 |
|
*/ |
778 |
|
final void signalWork() { |
779 |
< |
int ec; |
780 |
< |
UNSAFE.compareAndSwapInt(this, eventCountOffset, ec=eventCount, ec+1); |
781 |
< |
outer:for (;;) { |
782 |
< |
long top = eventWaiters; |
783 |
< |
ec = eventCount; |
779 |
> |
int c; |
780 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1); |
781 |
> |
long top; |
782 |
> |
while ((top = eventWaiters) != 0L) { |
783 |
> |
int ec = eventCount; |
784 |
> |
ForkJoinWorkerThread[] ws = workers; |
785 |
> |
int n = ws.length; |
786 |
|
for (;;) { |
787 |
< |
ForkJoinWorkerThread[] ws; ForkJoinWorkerThread w; |
788 |
< |
int id = (int)(top & WAITER_INDEX_MASK); |
789 |
< |
if (id <= 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec) |
754 |
< |
return; |
755 |
< |
if ((ws = workers).length < id || (w = ws[id - 1]) == null || |
756 |
< |
!UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
757 |
< |
top, top = w.nextWaiter)) |
758 |
< |
continue outer; // possibly stale; reread |
759 |
< |
LockSupport.unpark(w); |
760 |
< |
if (top != eventWaiters) // let someone else take over |
787 |
> |
int i = ((int)(top & WAITER_ID_MASK)) - 1; |
788 |
> |
int e = (int)(top >>> EVENT_COUNT_SHIFT); |
789 |
> |
if (i < 0 || e == ec) |
790 |
|
return; |
791 |
+ |
ForkJoinWorkerThread w; |
792 |
+ |
if (i < n && (w = ws[i]) != null && |
793 |
+ |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
794 |
+ |
top, top = w.nextWaiter)) { |
795 |
+ |
LockSupport.unpark(w); |
796 |
+ |
if (top != eventWaiters) // let someone else take over |
797 |
+ |
return; |
798 |
+ |
} |
799 |
+ |
else |
800 |
+ |
break; // possibly stale; reread |
801 |
|
} |
802 |
|
} |
803 |
|
} |
804 |
|
|
805 |
|
/** |
806 |
< |
* If worker is inactive, blocks until terminating or event count |
807 |
< |
* advances from last value held by worker; in any case helps |
769 |
< |
* release others. |
806 |
> |
* Blockss worker until terminating or event count |
807 |
> |
* advances from last value held by worker |
808 |
|
* |
809 |
|
* @param w the calling worker thread |
810 |
|
*/ |
811 |
|
private void eventSync(ForkJoinWorkerThread w) { |
812 |
< |
if (!w.active) { |
813 |
< |
int prev = w.lastEventCount; |
814 |
< |
long nextTop = (((long)prev << EVENT_COUNT_SHIFT) | |
815 |
< |
((long)(w.poolIndex + 1))); |
816 |
< |
long top; |
817 |
< |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
818 |
< |
(((int)(top = eventWaiters) & WAITER_INDEX_MASK) == 0 || |
819 |
< |
(int)(top >>> EVENT_COUNT_SHIFT) == prev) && |
820 |
< |
eventCount == prev) { |
821 |
< |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
822 |
< |
w.nextWaiter = top, nextTop)) { |
823 |
< |
accumulateStealCount(w); // transfer steals while idle |
824 |
< |
Thread.interrupted(); // clear/ignore interrupt |
825 |
< |
while (eventCount == prev) |
826 |
< |
w.doPark(); |
789 |
< |
break; |
790 |
< |
} |
812 |
> |
int wec = w.lastEventCount; |
813 |
> |
long nextTop = (((long)wec << EVENT_COUNT_SHIFT) | |
814 |
> |
((long)(w.poolIndex + 1))); |
815 |
> |
long top; |
816 |
> |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
817 |
> |
(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 || |
818 |
> |
(int)(top >>> EVENT_COUNT_SHIFT) == wec) && |
819 |
> |
eventCount == wec) { |
820 |
> |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
821 |
> |
w.nextWaiter = top, nextTop)) { |
822 |
> |
accumulateStealCount(w); // transfer steals while idle |
823 |
> |
Thread.interrupted(); // clear/ignore interrupt |
824 |
> |
while (eventCount == wec) |
825 |
> |
w.doPark(); |
826 |
> |
break; |
827 |
|
} |
792 |
– |
w.lastEventCount = eventCount; |
828 |
|
} |
829 |
< |
releaseWaiters(); |
829 |
> |
w.lastEventCount = eventCount; |
830 |
|
} |
831 |
|
|
832 |
|
/** |
847 |
|
* upon resume it rechecks to make sure that it is still needed. |
848 |
|
* |
849 |
|
* @param w the worker |
850 |
< |
* @param worked false if the worker scanned for work but didn't |
850 |
> |
* @param retries the number of scans by caller failing to find work |
851 |
|
* find any (in which case it may block waiting for work). |
852 |
|
*/ |
853 |
< |
final void preStep(ForkJoinWorkerThread w, boolean worked) { |
853 |
> |
final void preStep(ForkJoinWorkerThread w, int retries) { |
854 |
|
boolean active = w.active; |
855 |
< |
boolean inactivate = !worked & active; |
855 |
> |
boolean inactivate = active && retries > 0; |
856 |
|
for (;;) { |
857 |
< |
if (inactivate) { |
858 |
< |
int c = runState; |
859 |
< |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, |
860 |
< |
c, c - ONE_ACTIVE)) |
861 |
< |
inactivate = active = w.active = false; |
862 |
< |
} |
863 |
< |
int wc = workerCounts; |
864 |
< |
if ((wc & RUNNING_COUNT_MASK) <= parallelism) { |
865 |
< |
if (!worked) |
866 |
< |
eventSync(w); |
867 |
< |
return; |
857 |
> |
int rs, wc; |
858 |
> |
if (inactivate && |
859 |
> |
UNSAFE.compareAndSwapInt(this, runStateOffset, |
860 |
> |
rs = runState, rs - ONE_ACTIVE)) |
861 |
> |
inactivate = active = w.active = false; |
862 |
> |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) { |
863 |
> |
if (retries > 0) { |
864 |
> |
if (retries > 1 && !active) |
865 |
> |
eventSync(w); |
866 |
> |
releaseWaiters(); |
867 |
> |
} |
868 |
> |
break; |
869 |
|
} |
870 |
|
if (!(inactivate |= active) && // must inactivate to suspend |
871 |
|
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
872 |
|
wc, wc - ONE_RUNNING) && |
873 |
< |
!w.suspendAsSpare()) // false if trimmed |
874 |
< |
return; |
873 |
> |
!w.suspendAsSpare()) // false if trimmed |
874 |
> |
break; |
875 |
|
} |
876 |
|
} |
877 |
|
|
878 |
|
/** |
879 |
< |
* Adjusts counts and creates or resumes compensating threads for |
880 |
< |
* a worker about to block on task joinMe, returning early if |
881 |
< |
* joinMe becomes ready. First tries resuming an existing spare |
882 |
< |
* (which usually also avoids any count adjustment), but must then |
883 |
< |
* decrement running count to determine whether a new thread is |
884 |
< |
* needed. See above for fuller explanation. |
879 |
> |
* Awaits join of the given task if enough threads, or can resume |
880 |
> |
* or create a spare. Fails (in which case the given task might |
881 |
> |
* not be done) upon contention or lack of decision about |
882 |
> |
* blocking. |
883 |
> |
* |
884 |
> |
* We allow blocking if: |
885 |
> |
* |
886 |
> |
* 1. There would still be at least as many running threads as |
887 |
> |
* parallelism level if this thread blocks. |
888 |
> |
* |
889 |
> |
* 2. A spare is resumed to replace this worker. We tolerate |
890 |
> |
* races in the decision to replace when a spare is found. |
891 |
> |
* This may release too many, but if so, the superfluous ones |
892 |
> |
* will re-suspend via preStep(). |
893 |
> |
* |
894 |
> |
* 3. After #spares repeated retries, there are fewer than #spare |
895 |
> |
* threads not running. We allow this slack to avoid hysteresis |
896 |
> |
* and as a hedge against lag/uncertainty of running count |
897 |
> |
* estimates when signalling or unblocking stalls. |
898 |
> |
* |
899 |
> |
* 4. All existing workers are busy (as rechecked via #spares |
900 |
> |
* repeated retries by caller) and a new spare is created. |
901 |
> |
* |
902 |
> |
* If none of the above hold, we escape out by re-incrementing |
903 |
> |
* count and returning to caller, which can retry later. |
904 |
> |
* |
905 |
> |
* @param joinMe the task to join |
906 |
> |
* @param retries the number of calls to this method for this join |
907 |
|
*/ |
908 |
< |
final void preJoin(ForkJoinTask<?> joinMe) { |
909 |
< |
boolean dec = false; // true when running count decremented |
910 |
< |
for (;;) { |
911 |
< |
releaseWaiters(); // help other threads progress |
912 |
< |
|
913 |
< |
if (joinMe.status < 0) // surround spare search with done checks |
914 |
< |
return; |
915 |
< |
ForkJoinWorkerThread spare = null; |
916 |
< |
for (ForkJoinWorkerThread w : workers) { |
917 |
< |
if (w != null && w.isSuspended()) { |
918 |
< |
spare = w; |
919 |
< |
break; |
908 |
> |
final void tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) { |
909 |
> |
int pc = parallelism; |
910 |
> |
boolean running = true; // false when running count decremented |
911 |
> |
outer:while (joinMe.status >= 0) { |
912 |
> |
int wc = workerCounts; |
913 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
914 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
915 |
> |
if (running) { // replace with spare or decrement count |
916 |
> |
if (rc <= pc && tc > pc && |
917 |
> |
(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) { |
918 |
> |
ForkJoinWorkerThread[] ws = workers; // search for spare |
919 |
> |
int nws = ws.length; |
920 |
> |
for (int i = 0; i < nws; ++i) { |
921 |
> |
ForkJoinWorkerThread w = ws[i]; |
922 |
> |
if (w != null && w.isSuspended()) { |
923 |
> |
if ((workerCounts & RUNNING_COUNT_MASK) > pc) |
924 |
> |
continue outer; |
925 |
> |
if (joinMe.status < 0) |
926 |
> |
break outer; |
927 |
> |
if (w.tryResumeSpare()) { |
928 |
> |
running = false; |
929 |
> |
break outer; |
930 |
> |
} |
931 |
> |
continue outer; // rescan on failure to resume |
932 |
> |
} |
933 |
> |
} |
934 |
|
} |
935 |
< |
} |
936 |
< |
if (joinMe.status < 0) |
937 |
< |
return; |
938 |
< |
|
939 |
< |
if (spare != null && spare.tryUnsuspend()) { |
940 |
< |
if (dec || joinMe.requestSignal() < 0) { |
941 |
< |
int c; |
942 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, |
943 |
< |
workerCountsOffset, |
944 |
< |
c = workerCounts, |
945 |
< |
c + ONE_RUNNING)); |
946 |
< |
} // else no net count change |
947 |
< |
LockSupport.unpark(spare); |
948 |
< |
return; |
949 |
< |
} |
878 |
< |
|
879 |
< |
int wc = workerCounts; // decrement running count |
880 |
< |
if (!dec && (wc & RUNNING_COUNT_MASK) != 0 && |
881 |
< |
(dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
882 |
< |
wc, wc -= ONE_RUNNING)) && |
883 |
< |
joinMe.requestSignal() < 0) { // cannot block |
884 |
< |
int c; // back out |
885 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, |
886 |
< |
workerCountsOffset, |
887 |
< |
c = workerCounts, |
888 |
< |
c + ONE_RUNNING)); |
889 |
< |
return; |
890 |
< |
} |
891 |
< |
|
892 |
< |
if (dec) { |
893 |
< |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
894 |
< |
int pc = parallelism; |
895 |
< |
int dc = pc - (wc & RUNNING_COUNT_MASK); // deficit count |
896 |
< |
if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) || |
897 |
< |
!maintainsParallelism)) || |
898 |
< |
tc >= maxPoolSize) // cannot add |
899 |
< |
return; |
900 |
< |
if (spare == null && |
935 |
> |
if ((rc <= pc && (rc == 0 || --retries < 0)) || // no retry |
936 |
> |
joinMe.status < 0) |
937 |
> |
break; |
938 |
> |
if (workerCounts == wc && |
939 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
940 |
> |
wc, wc - ONE_RUNNING)) |
941 |
> |
running = false; |
942 |
> |
} |
943 |
> |
else { // allow blocking if enough threads |
944 |
> |
int sc = tc - pc + 1; // = spares, plus the one to add |
945 |
> |
if (sc > 0 && rc > 0 && rc >= pc - sc && rc > pc - retries) |
946 |
> |
break; |
947 |
> |
if (--retries > sc && tc < MAX_THREADS && |
948 |
> |
tc == (runState & ACTIVE_COUNT_MASK) && |
949 |
> |
workerCounts == wc && |
950 |
|
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
951 |
|
wc + (ONE_RUNNING|ONE_TOTAL))) { |
952 |
|
addWorker(); |
953 |
< |
return; |
953 |
> |
break; |
954 |
> |
} |
955 |
> |
if (workerCounts == wc && |
956 |
> |
UNSAFE.compareAndSwapInt (this, workerCountsOffset, |
957 |
> |
wc, wc + ONE_RUNNING)) { |
958 |
> |
running = true; // back out; allow retry |
959 |
> |
break; |
960 |
|
} |
961 |
|
} |
962 |
|
} |
963 |
+ |
if (!running) { // can block |
964 |
+ |
int c; // to inline incrementRunningCount |
965 |
+ |
joinMe.internalAwaitDone(); |
966 |
+ |
do {} while (!UNSAFE.compareAndSwapInt |
967 |
+ |
(this, workerCountsOffset, |
968 |
+ |
c = workerCounts, c + ONE_RUNNING)); |
969 |
+ |
} |
970 |
|
} |
971 |
|
|
972 |
|
/** |
973 |
< |
* Same idea as preJoin but with too many differing details to |
974 |
< |
* integrate: There are no task-based signal counts, and only one |
975 |
< |
* way to do the actual blocking. So for simplicity it is directly |
914 |
< |
* incorporated into this method. |
973 |
> |
* Same idea as (and shares many code snippets with) tryAwaitJoin, |
974 |
> |
* but self-contained because there are no caller retries. |
975 |
> |
* TODO: Rework to use simpler API. |
976 |
|
*/ |
977 |
< |
final void doBlock(ManagedBlocker blocker, boolean maintainPar) |
977 |
> |
final void awaitBlocker(ManagedBlocker blocker) |
978 |
|
throws InterruptedException { |
979 |
< |
maintainPar &= maintainsParallelism; // override |
980 |
< |
boolean dec = false; |
981 |
< |
boolean done = false; |
982 |
< |
for (;;) { |
983 |
< |
releaseWaiters(); |
984 |
< |
if (done = blocker.isReleasable()) |
985 |
< |
break; |
986 |
< |
ForkJoinWorkerThread spare = null; |
987 |
< |
for (ForkJoinWorkerThread w : workers) { |
988 |
< |
if (w != null && w.isSuspended()) { |
989 |
< |
spare = w; |
990 |
< |
break; |
979 |
> |
int pc = parallelism; |
980 |
> |
boolean running = true; |
981 |
> |
int retries = 0; |
982 |
> |
boolean done; |
983 |
> |
outer:while (!(done = blocker.isReleasable())) { |
984 |
> |
int wc = workerCounts; |
985 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
986 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
987 |
> |
if (running) { |
988 |
> |
if (rc <= pc && tc > pc && |
989 |
> |
(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) { |
990 |
> |
ForkJoinWorkerThread[] ws = workers; |
991 |
> |
int nws = ws.length; |
992 |
> |
for (int i = 0; i < nws; ++i) { |
993 |
> |
ForkJoinWorkerThread w = ws[i]; |
994 |
> |
if (w != null && w.isSuspended()) { |
995 |
> |
if ((workerCounts & RUNNING_COUNT_MASK) > pc) |
996 |
> |
continue outer; |
997 |
> |
if (done = blocker.isReleasable()) |
998 |
> |
break outer; |
999 |
> |
if (w.tryResumeSpare()) { |
1000 |
> |
running = false; |
1001 |
> |
break outer; |
1002 |
> |
} |
1003 |
> |
continue outer; |
1004 |
> |
} |
1005 |
> |
} |
1006 |
> |
if (done = blocker.isReleasable()) |
1007 |
> |
break; |
1008 |
> |
} |
1009 |
> |
if (rc > 0 && workerCounts == wc && |
1010 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1011 |
> |
wc, wc - ONE_RUNNING)) { |
1012 |
> |
running = false; |
1013 |
> |
if (rc > pc) |
1014 |
> |
break; |
1015 |
|
} |
1016 |
|
} |
1017 |
< |
if (done = blocker.isReleasable()) |
1017 |
> |
else if (rc >= pc) |
1018 |
|
break; |
1019 |
< |
if (spare != null && spare.tryUnsuspend()) { |
1020 |
< |
if (dec) { |
1021 |
< |
int c; |
1022 |
< |
do {} while (!UNSAFE.compareAndSwapInt(this, |
1023 |
< |
workerCountsOffset, |
1024 |
< |
c = workerCounts, |
940 |
< |
c + ONE_RUNNING)); |
941 |
< |
} |
942 |
< |
LockSupport.unpark(spare); |
1019 |
> |
else if (tc < MAX_THREADS && |
1020 |
> |
tc == (runState & ACTIVE_COUNT_MASK) && |
1021 |
> |
workerCounts == wc && |
1022 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
1023 |
> |
wc + (ONE_RUNNING|ONE_TOTAL))) { |
1024 |
> |
addWorker(); |
1025 |
|
break; |
1026 |
|
} |
1027 |
< |
int wc = workerCounts; |
1028 |
< |
if (!dec && (wc & RUNNING_COUNT_MASK) != 0) |
1029 |
< |
dec = UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1030 |
< |
wc, wc -= ONE_RUNNING); |
1031 |
< |
if (dec) { |
1032 |
< |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
951 |
< |
int pc = parallelism; |
952 |
< |
int dc = pc - (wc & RUNNING_COUNT_MASK); |
953 |
< |
if ((dc < pc && (dc <= 0 || (dc * dc < (tc - pc) * pc) || |
954 |
< |
!maintainPar)) || |
955 |
< |
tc >= maxPoolSize) |
956 |
< |
break; |
957 |
< |
if (spare == null && |
958 |
< |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
959 |
< |
wc + (ONE_RUNNING|ONE_TOTAL))){ |
960 |
< |
addWorker(); |
961 |
< |
break; |
962 |
< |
} |
1027 |
> |
else if (workerCounts == wc && |
1028 |
> |
UNSAFE.compareAndSwapInt (this, workerCountsOffset, |
1029 |
> |
wc, wc + ONE_RUNNING)) { |
1030 |
> |
Thread.yield(); |
1031 |
> |
++retries; |
1032 |
> |
running = true; // allow rescan |
1033 |
|
} |
1034 |
|
} |
1035 |
|
|
1037 |
|
if (!done) |
1038 |
|
do {} while (!blocker.isReleasable() && !blocker.block()); |
1039 |
|
} finally { |
1040 |
< |
if (dec) { |
1040 |
> |
if (!running) { |
1041 |
|
int c; |
972 |
– |
do {} while (!UNSAFE.compareAndSwapInt(this, |
973 |
– |
workerCountsOffset, |
974 |
– |
c = workerCounts, |
975 |
– |
c + ONE_RUNNING)); |
976 |
– |
} |
977 |
– |
} |
978 |
– |
} |
979 |
– |
|
980 |
– |
/** |
981 |
– |
* Unless there are not enough other running threads, adjusts |
982 |
– |
* counts for a a worker in performing helpJoin that cannot find |
983 |
– |
* any work, so that this worker can now block. |
984 |
– |
* |
985 |
– |
* @return true if worker may block |
986 |
– |
*/ |
987 |
– |
final boolean preBlockHelpingJoin(ForkJoinTask<?> joinMe) { |
988 |
– |
while (joinMe.status >= 0) { |
989 |
– |
releaseWaiters(); // help other threads progress |
990 |
– |
|
991 |
– |
// if a spare exists, resume it to maintain parallelism level |
992 |
– |
if ((workerCounts & RUNNING_COUNT_MASK) <= parallelism) { |
993 |
– |
ForkJoinWorkerThread spare = null; |
994 |
– |
for (ForkJoinWorkerThread w : workers) { |
995 |
– |
if (w != null && w.isSuspended()) { |
996 |
– |
spare = w; |
997 |
– |
break; |
998 |
– |
} |
999 |
– |
} |
1000 |
– |
if (joinMe.status < 0) |
1001 |
– |
break; |
1002 |
– |
if (spare != null) { |
1003 |
– |
if (spare.tryUnsuspend()) { |
1004 |
– |
boolean canBlock = true; |
1005 |
– |
if (joinMe.requestSignal() < 0) { |
1006 |
– |
canBlock = false; // already done |
1007 |
– |
int c; |
1008 |
– |
do {} while (!UNSAFE.compareAndSwapInt |
1009 |
– |
(this, workerCountsOffset, |
1010 |
– |
c = workerCounts, c + ONE_RUNNING)); |
1011 |
– |
} |
1012 |
– |
LockSupport.unpark(spare); |
1013 |
– |
return canBlock; |
1014 |
– |
} |
1015 |
– |
continue; // recheck -- another spare may exist |
1016 |
– |
} |
1017 |
– |
} |
1018 |
– |
|
1019 |
– |
int wc = workerCounts; // reread to shorten CAS window |
1020 |
– |
int rc = wc & RUNNING_COUNT_MASK; |
1021 |
– |
if (rc <= 2) // keep this and at most one other thread alive |
1022 |
– |
break; |
1023 |
– |
|
1024 |
– |
if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1025 |
– |
wc, wc - ONE_RUNNING)) { |
1026 |
– |
if (joinMe.requestSignal() >= 0) |
1027 |
– |
return true; |
1028 |
– |
int c; // back out |
1042 |
|
do {} while (!UNSAFE.compareAndSwapInt |
1043 |
|
(this, workerCountsOffset, |
1044 |
|
c = workerCounts, c + ONE_RUNNING)); |
1032 |
– |
break; |
1045 |
|
} |
1046 |
|
} |
1035 |
– |
return false; |
1047 |
|
} |
1048 |
|
|
1049 |
|
/** |
1067 |
|
// Finish now if all threads terminated; else in some subsequent call |
1068 |
|
if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) { |
1069 |
|
advanceRunLevel(TERMINATED); |
1070 |
< |
terminationLatch.countDown(); |
1070 |
> |
termination.arrive(); |
1071 |
|
} |
1072 |
|
return true; |
1073 |
|
} |
1076 |
|
* Actions on transition to TERMINATING |
1077 |
|
*/ |
1078 |
|
private void startTerminating() { |
1079 |
< |
// Clear out and cancel submissions, ignoring exceptions |
1079 |
> |
for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers |
1080 |
> |
cancelSubmissions(); |
1081 |
> |
shutdownWorkers(); |
1082 |
> |
cancelWorkerTasks(); |
1083 |
> |
signalEvent(); |
1084 |
> |
interruptWorkers(); |
1085 |
> |
} |
1086 |
> |
} |
1087 |
> |
|
1088 |
> |
/** |
1089 |
> |
* Clear out and cancel submissions, ignoring exceptions |
1090 |
> |
*/ |
1091 |
> |
private void cancelSubmissions() { |
1092 |
|
ForkJoinTask<?> task; |
1093 |
|
while ((task = submissionQueue.poll()) != null) { |
1094 |
|
try { |
1096 |
|
} catch (Throwable ignore) { |
1097 |
|
} |
1098 |
|
} |
1099 |
< |
// Propagate run level |
1100 |
< |
for (ForkJoinWorkerThread w : workers) { |
1099 |
> |
} |
1100 |
> |
|
1101 |
> |
/** |
1102 |
> |
* Sets all worker run states to at least shutdown, |
1103 |
> |
* also resuming suspended workers |
1104 |
> |
*/ |
1105 |
> |
private void shutdownWorkers() { |
1106 |
> |
ForkJoinWorkerThread[] ws = workers; |
1107 |
> |
int nws = ws.length; |
1108 |
> |
for (int i = 0; i < nws; ++i) { |
1109 |
> |
ForkJoinWorkerThread w = ws[i]; |
1110 |
|
if (w != null) |
1111 |
< |
w.shutdown(); // also resumes suspended workers |
1111 |
> |
w.shutdown(); |
1112 |
|
} |
1113 |
< |
// Ensure no straggling local tasks |
1114 |
< |
for (ForkJoinWorkerThread w : workers) { |
1113 |
> |
} |
1114 |
> |
|
1115 |
> |
/** |
1116 |
> |
* Clears out and cancels all locally queued tasks |
1117 |
> |
*/ |
1118 |
> |
private void cancelWorkerTasks() { |
1119 |
> |
ForkJoinWorkerThread[] ws = workers; |
1120 |
> |
int nws = ws.length; |
1121 |
> |
for (int i = 0; i < nws; ++i) { |
1122 |
> |
ForkJoinWorkerThread w = ws[i]; |
1123 |
|
if (w != null) |
1124 |
|
w.cancelTasks(); |
1125 |
|
} |
1126 |
< |
// Wake up idle workers |
1127 |
< |
advanceEventCount(); |
1128 |
< |
releaseWaiters(); |
1129 |
< |
// Unstick pending joins |
1130 |
< |
for (ForkJoinWorkerThread w : workers) { |
1126 |
> |
} |
1127 |
> |
|
1128 |
> |
/** |
1129 |
> |
* Unsticks all workers blocked on joins etc |
1130 |
> |
*/ |
1131 |
> |
private void interruptWorkers() { |
1132 |
> |
ForkJoinWorkerThread[] ws = workers; |
1133 |
> |
int nws = ws.length; |
1134 |
> |
for (int i = 0; i < nws; ++i) { |
1135 |
> |
ForkJoinWorkerThread w = ws[i]; |
1136 |
|
if (w != null && !w.isTerminated()) { |
1137 |
|
try { |
1138 |
|
w.interrupt(); |
1170 |
|
* active thread. |
1171 |
|
*/ |
1172 |
|
final int idlePerActive() { |
1173 |
+ |
int pc = parallelism; // use parallelism, not rc |
1174 |
|
int ac = runState; // no mask -- artifically boosts during shutdown |
1129 |
– |
int pc = parallelism; // use targeted parallelism, not rc |
1175 |
|
// Use exact results for small values, saturate past 4 |
1176 |
|
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1177 |
|
} |
1182 |
|
|
1183 |
|
/** |
1184 |
|
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1185 |
< |
* java.lang.Runtime#availableProcessors}, and using the {@linkplain |
1186 |
< |
* #defaultForkJoinWorkerThreadFactory default thread factory}. |
1185 |
> |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
1186 |
> |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1187 |
> |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1188 |
|
* |
1189 |
|
* @throws SecurityException if a security manager exists and |
1190 |
|
* the caller is not permitted to modify threads |
1193 |
|
*/ |
1194 |
|
public ForkJoinPool() { |
1195 |
|
this(Runtime.getRuntime().availableProcessors(), |
1196 |
< |
defaultForkJoinWorkerThreadFactory); |
1196 |
> |
defaultForkJoinWorkerThreadFactory, null, false); |
1197 |
|
} |
1198 |
|
|
1199 |
|
/** |
1200 |
|
* Creates a {@code ForkJoinPool} with the indicated parallelism |
1201 |
< |
* level and using the {@linkplain |
1202 |
< |
* #defaultForkJoinWorkerThreadFactory default thread factory}. |
1201 |
> |
* level, the {@linkplain |
1202 |
> |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1203 |
> |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1204 |
|
* |
1205 |
|
* @param parallelism the parallelism level |
1206 |
|
* @throws IllegalArgumentException if parallelism less than or |
1211 |
|
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1212 |
|
*/ |
1213 |
|
public ForkJoinPool(int parallelism) { |
1214 |
< |
this(parallelism, defaultForkJoinWorkerThreadFactory); |
1214 |
> |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
1215 |
|
} |
1216 |
|
|
1217 |
|
/** |
1218 |
< |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1172 |
< |
* java.lang.Runtime#availableProcessors}, and using the given |
1173 |
< |
* thread factory. |
1218 |
> |
* Creates a {@code ForkJoinPool} with the given parameters. |
1219 |
|
* |
1220 |
< |
* @param factory the factory for creating new threads |
1221 |
< |
* @throws NullPointerException if the factory is null |
1222 |
< |
* @throws SecurityException if a security manager exists and |
1223 |
< |
* the caller is not permitted to modify threads |
1224 |
< |
* because it does not hold {@link |
1225 |
< |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1226 |
< |
*/ |
1227 |
< |
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
1228 |
< |
this(Runtime.getRuntime().availableProcessors(), factory); |
1229 |
< |
} |
1230 |
< |
|
1231 |
< |
/** |
1232 |
< |
* Creates a {@code ForkJoinPool} with the given parallelism and |
1188 |
< |
* thread factory. |
1189 |
< |
* |
1190 |
< |
* @param parallelism the parallelism level |
1191 |
< |
* @param factory the factory for creating new threads |
1220 |
> |
* @param parallelism the parallelism level. For default value, |
1221 |
> |
* use {@link java.lang.Runtime#availableProcessors}. |
1222 |
> |
* @param factory the factory for creating new threads. For default value, |
1223 |
> |
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1224 |
> |
* @param handler the handler for internal worker threads that |
1225 |
> |
* terminate due to unrecoverable errors encountered while executing |
1226 |
> |
* tasks. For default value, use <code>null</code>. |
1227 |
> |
* @param asyncMode if true, |
1228 |
> |
* establishes local first-in-first-out scheduling mode for forked |
1229 |
> |
* tasks that are never joined. This mode may be more appropriate |
1230 |
> |
* than default locally stack-based mode in applications in which |
1231 |
> |
* worker threads only process event-style asynchronous tasks. |
1232 |
> |
* For default value, use <code>false</code>. |
1233 |
|
* @throws IllegalArgumentException if parallelism less than or |
1234 |
|
* equal to zero, or greater than implementation limit |
1235 |
|
* @throws NullPointerException if the factory is null |
1238 |
|
* because it does not hold {@link |
1239 |
|
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1240 |
|
*/ |
1241 |
< |
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
1241 |
> |
public ForkJoinPool(int parallelism, |
1242 |
> |
ForkJoinWorkerThreadFactory factory, |
1243 |
> |
Thread.UncaughtExceptionHandler handler, |
1244 |
> |
boolean asyncMode) { |
1245 |
|
checkPermission(); |
1246 |
|
if (factory == null) |
1247 |
|
throw new NullPointerException(); |
1248 |
|
if (parallelism <= 0 || parallelism > MAX_THREADS) |
1249 |
|
throw new IllegalArgumentException(); |
1206 |
– |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1207 |
– |
int arraySize = initialArraySizeFor(parallelism); |
1250 |
|
this.parallelism = parallelism; |
1251 |
|
this.factory = factory; |
1252 |
< |
this.maxPoolSize = MAX_THREADS; |
1253 |
< |
this.maintainsParallelism = true; |
1252 |
> |
this.ueh = handler; |
1253 |
> |
this.locallyFifo = asyncMode; |
1254 |
> |
int arraySize = initialArraySizeFor(parallelism); |
1255 |
|
this.workers = new ForkJoinWorkerThread[arraySize]; |
1256 |
|
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
1257 |
|
this.workerLock = new ReentrantLock(); |
1258 |
< |
this.terminationLatch = new CountDownLatch(1); |
1259 |
< |
// Start first worker; remaining workers added upon first submission |
1217 |
< |
workerCounts = ONE_RUNNING | ONE_TOTAL; |
1218 |
< |
addWorker(); |
1258 |
> |
this.termination = new Phaser(1); |
1259 |
> |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1260 |
|
} |
1261 |
|
|
1262 |
|
/** |
1284 |
|
if (runState >= SHUTDOWN) |
1285 |
|
throw new RejectedExecutionException(); |
1286 |
|
submissionQueue.offer(task); |
1287 |
< |
advanceEventCount(); |
1288 |
< |
releaseWaiters(); |
1248 |
< |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) < parallelism) |
1249 |
< |
ensureEnoughTotalWorkers(); |
1287 |
> |
signalEvent(); |
1288 |
> |
ensureEnoughTotalWorkers(); |
1289 |
|
} |
1290 |
|
|
1291 |
|
/** |
1292 |
|
* Performs the given task, returning its result upon completion. |
1293 |
+ |
* If the caller is already engaged in a fork/join computation in |
1294 |
+ |
* the current pool, this method is equivalent in effect to |
1295 |
+ |
* {@link ForkJoinTask#invoke}. |
1296 |
|
* |
1297 |
|
* @param task the task |
1298 |
|
* @return the task's result |
1307 |
|
|
1308 |
|
/** |
1309 |
|
* Arranges for (asynchronous) execution of the given task. |
1310 |
+ |
* If the caller is already engaged in a fork/join computation in |
1311 |
+ |
* the current pool, this method is equivalent in effect to |
1312 |
+ |
* {@link ForkJoinTask#fork}. |
1313 |
|
* |
1314 |
|
* @param task the task |
1315 |
|
* @throws NullPointerException if the task is null |
1337 |
|
} |
1338 |
|
|
1339 |
|
/** |
1340 |
+ |
* Submits a ForkJoinTask for execution. |
1341 |
+ |
* If the caller is already engaged in a fork/join computation in |
1342 |
+ |
* the current pool, this method is equivalent in effect to |
1343 |
+ |
* {@link ForkJoinTask#fork}. |
1344 |
+ |
* |
1345 |
+ |
* @param task the task to submit |
1346 |
+ |
* @return the task |
1347 |
+ |
* @throws NullPointerException if the task is null |
1348 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1349 |
+ |
* scheduled for execution |
1350 |
+ |
*/ |
1351 |
+ |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1352 |
+ |
doSubmit(task); |
1353 |
+ |
return task; |
1354 |
+ |
} |
1355 |
+ |
|
1356 |
+ |
/** |
1357 |
|
* @throws NullPointerException if the task is null |
1358 |
|
* @throws RejectedExecutionException if the task cannot be |
1359 |
|
* scheduled for execution |
1391 |
|
} |
1392 |
|
|
1393 |
|
/** |
1332 |
– |
* Submits a ForkJoinTask for execution. |
1333 |
– |
* |
1334 |
– |
* @param task the task to submit |
1335 |
– |
* @return the task |
1336 |
– |
* @throws NullPointerException if the task is null |
1337 |
– |
* @throws RejectedExecutionException if the task cannot be |
1338 |
– |
* scheduled for execution |
1339 |
– |
*/ |
1340 |
– |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1341 |
– |
doSubmit(task); |
1342 |
– |
return task; |
1343 |
– |
} |
1344 |
– |
|
1345 |
– |
/** |
1394 |
|
* @throws NullPointerException {@inheritDoc} |
1395 |
|
* @throws RejectedExecutionException {@inheritDoc} |
1396 |
|
*/ |
1432 |
|
* @return the handler, or {@code null} if none |
1433 |
|
*/ |
1434 |
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
1387 |
– |
workerCountReadFence(); |
1435 |
|
return ueh; |
1436 |
|
} |
1437 |
|
|
1438 |
|
/** |
1392 |
– |
* Sets the handler for internal worker threads that terminate due |
1393 |
– |
* to unrecoverable errors encountered while executing tasks. |
1394 |
– |
* Unless set, the current default or ThreadGroup handler is used |
1395 |
– |
* as handler. |
1396 |
– |
* |
1397 |
– |
* @param h the new handler |
1398 |
– |
* @return the old handler, or {@code null} if none |
1399 |
– |
* @throws SecurityException if a security manager exists and |
1400 |
– |
* the caller is not permitted to modify threads |
1401 |
– |
* because it does not hold {@link |
1402 |
– |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1403 |
– |
*/ |
1404 |
– |
public Thread.UncaughtExceptionHandler |
1405 |
– |
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
1406 |
– |
checkPermission(); |
1407 |
– |
workerCountReadFence(); |
1408 |
– |
Thread.UncaughtExceptionHandler old = ueh; |
1409 |
– |
if (h != old) { |
1410 |
– |
ueh = h; |
1411 |
– |
workerCountWriteFence(); |
1412 |
– |
for (ForkJoinWorkerThread w : workers) { |
1413 |
– |
if (w != null) |
1414 |
– |
w.setUncaughtExceptionHandler(h); |
1415 |
– |
} |
1416 |
– |
} |
1417 |
– |
return old; |
1418 |
– |
} |
1419 |
– |
|
1420 |
– |
/** |
1421 |
– |
* Sets the target parallelism level of this pool. |
1422 |
– |
* |
1423 |
– |
* @param parallelism the target parallelism |
1424 |
– |
* @throws IllegalArgumentException if parallelism less than or |
1425 |
– |
* equal to zero or greater than maximum size bounds |
1426 |
– |
* @throws SecurityException if a security manager exists and |
1427 |
– |
* the caller is not permitted to modify threads |
1428 |
– |
* because it does not hold {@link |
1429 |
– |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1430 |
– |
*/ |
1431 |
– |
public void setParallelism(int parallelism) { |
1432 |
– |
checkPermission(); |
1433 |
– |
if (parallelism <= 0 || parallelism > maxPoolSize) |
1434 |
– |
throw new IllegalArgumentException(); |
1435 |
– |
workerCountReadFence(); |
1436 |
– |
int pc = this.parallelism; |
1437 |
– |
if (pc != parallelism) { |
1438 |
– |
this.parallelism = parallelism; |
1439 |
– |
workerCountWriteFence(); |
1440 |
– |
// Release spares. If too many, some will die after re-suspend |
1441 |
– |
for (ForkJoinWorkerThread w : workers) { |
1442 |
– |
if (w != null && w.tryUnsuspend()) { |
1443 |
– |
updateRunningCount(1); |
1444 |
– |
LockSupport.unpark(w); |
1445 |
– |
} |
1446 |
– |
} |
1447 |
– |
ensureEnoughTotalWorkers(); |
1448 |
– |
advanceEventCount(); |
1449 |
– |
releaseWaiters(); // force config recheck by existing workers |
1450 |
– |
} |
1451 |
– |
} |
1452 |
– |
|
1453 |
– |
/** |
1439 |
|
* Returns the targeted parallelism level of this pool. |
1440 |
|
* |
1441 |
|
* @return the targeted parallelism level of this pool |
1442 |
|
*/ |
1443 |
|
public int getParallelism() { |
1459 |
– |
// workerCountReadFence(); // inlined below |
1460 |
– |
int ignore = workerCounts; |
1444 |
|
return parallelism; |
1445 |
|
} |
1446 |
|
|
1457 |
|
} |
1458 |
|
|
1459 |
|
/** |
1477 |
– |
* Returns the maximum number of threads allowed to exist in the |
1478 |
– |
* pool. Unless set using {@link #setMaximumPoolSize}, the |
1479 |
– |
* maximum is an implementation-defined value designed only to |
1480 |
– |
* prevent runaway growth. |
1481 |
– |
* |
1482 |
– |
* @return the maximum |
1483 |
– |
*/ |
1484 |
– |
public int getMaximumPoolSize() { |
1485 |
– |
workerCountReadFence(); |
1486 |
– |
return maxPoolSize; |
1487 |
– |
} |
1488 |
– |
|
1489 |
– |
/** |
1490 |
– |
* Sets the maximum number of threads allowed to exist in the |
1491 |
– |
* pool. The given value should normally be greater than or equal |
1492 |
– |
* to the {@link #getParallelism parallelism} level. Setting this |
1493 |
– |
* value has no effect on current pool size. It controls |
1494 |
– |
* construction of new threads. The use of this method may cause |
1495 |
– |
* tasks that intrinsically require extra threads for dependent |
1496 |
– |
* computations to indefinitely stall. If you are instead trying |
1497 |
– |
* to minimize internal thread creation, consider setting {link |
1498 |
– |
* #setMaintainsParallelism} as false. |
1499 |
– |
* |
1500 |
– |
* @throws IllegalArgumentException if negative or greater than |
1501 |
– |
* internal implementation limit |
1502 |
– |
*/ |
1503 |
– |
public void setMaximumPoolSize(int newMax) { |
1504 |
– |
if (newMax < 0 || newMax > MAX_THREADS) |
1505 |
– |
throw new IllegalArgumentException(); |
1506 |
– |
maxPoolSize = newMax; |
1507 |
– |
workerCountWriteFence(); |
1508 |
– |
} |
1509 |
– |
|
1510 |
– |
/** |
1511 |
– |
* Returns {@code true} if this pool dynamically maintains its |
1512 |
– |
* target parallelism level. If false, new threads are added only |
1513 |
– |
* to avoid possible starvation. This setting is by default true. |
1514 |
– |
* |
1515 |
– |
* @return {@code true} if maintains parallelism |
1516 |
– |
*/ |
1517 |
– |
public boolean getMaintainsParallelism() { |
1518 |
– |
workerCountReadFence(); |
1519 |
– |
return maintainsParallelism; |
1520 |
– |
} |
1521 |
– |
|
1522 |
– |
/** |
1523 |
– |
* Sets whether this pool dynamically maintains its target |
1524 |
– |
* parallelism level. If false, new threads are added only to |
1525 |
– |
* avoid possible starvation. |
1526 |
– |
* |
1527 |
– |
* @param enable {@code true} to maintain parallelism |
1528 |
– |
*/ |
1529 |
– |
public void setMaintainsParallelism(boolean enable) { |
1530 |
– |
maintainsParallelism = enable; |
1531 |
– |
workerCountWriteFence(); |
1532 |
– |
} |
1533 |
– |
|
1534 |
– |
/** |
1535 |
– |
* Establishes local first-in-first-out scheduling mode for forked |
1536 |
– |
* tasks that are never joined. This mode may be more appropriate |
1537 |
– |
* than default locally stack-based mode in applications in which |
1538 |
– |
* worker threads only process asynchronous tasks. This method is |
1539 |
– |
* designed to be invoked only when the pool is quiescent, and |
1540 |
– |
* typically only before any tasks are submitted. The effects of |
1541 |
– |
* invocations at other times may be unpredictable. |
1542 |
– |
* |
1543 |
– |
* @param async if {@code true}, use locally FIFO scheduling |
1544 |
– |
* @return the previous mode |
1545 |
– |
* @see #getAsyncMode |
1546 |
– |
*/ |
1547 |
– |
public boolean setAsyncMode(boolean async) { |
1548 |
– |
workerCountReadFence(); |
1549 |
– |
boolean oldMode = locallyFifo; |
1550 |
– |
if (oldMode != async) { |
1551 |
– |
locallyFifo = async; |
1552 |
– |
workerCountWriteFence(); |
1553 |
– |
for (ForkJoinWorkerThread w : workers) { |
1554 |
– |
if (w != null) |
1555 |
– |
w.setAsyncMode(async); |
1556 |
– |
} |
1557 |
– |
} |
1558 |
– |
return oldMode; |
1559 |
– |
} |
1560 |
– |
|
1561 |
– |
/** |
1460 |
|
* Returns {@code true} if this pool uses local first-in-first-out |
1461 |
|
* scheduling mode for forked tasks that are never joined. |
1462 |
|
* |
1463 |
|
* @return {@code true} if this pool uses async mode |
1566 |
– |
* @see #setAsyncMode |
1464 |
|
*/ |
1465 |
|
public boolean getAsyncMode() { |
1569 |
– |
workerCountReadFence(); |
1466 |
|
return locallyFifo; |
1467 |
|
} |
1468 |
|
|
1531 |
|
*/ |
1532 |
|
public long getQueuedTaskCount() { |
1533 |
|
long count = 0; |
1534 |
< |
for (ForkJoinWorkerThread w : workers) { |
1534 |
> |
ForkJoinWorkerThread[] ws = workers; |
1535 |
> |
int nws = ws.length; |
1536 |
> |
for (int i = 0; i < nws; ++i) { |
1537 |
> |
ForkJoinWorkerThread w = ws[i]; |
1538 |
|
if (w != null) |
1539 |
|
count += w.getQueueSize(); |
1540 |
|
} |
1592 |
|
*/ |
1593 |
|
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1594 |
|
int n = submissionQueue.drainTo(c); |
1595 |
< |
for (ForkJoinWorkerThread w : workers) { |
1595 |
> |
ForkJoinWorkerThread[] ws = workers; |
1596 |
> |
int nws = ws.length; |
1597 |
> |
for (int i = 0; i < nws; ++i) { |
1598 |
> |
ForkJoinWorkerThread w = ws[i]; |
1599 |
|
if (w != null) |
1600 |
|
n += w.drainTasksTo(c); |
1601 |
|
} |
1603 |
|
} |
1604 |
|
|
1605 |
|
/** |
1606 |
+ |
* Returns count of total parks by existing workers. |
1607 |
+ |
* Used during development only since not meaningful to users. |
1608 |
+ |
*/ |
1609 |
+ |
private int collectParkCount() { |
1610 |
+ |
int count = 0; |
1611 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1612 |
+ |
int nws = ws.length; |
1613 |
+ |
for (int i = 0; i < nws; ++i) { |
1614 |
+ |
ForkJoinWorkerThread w = ws[i]; |
1615 |
+ |
if (w != null) |
1616 |
+ |
count += w.parkCount; |
1617 |
+ |
} |
1618 |
+ |
return count; |
1619 |
+ |
} |
1620 |
+ |
|
1621 |
+ |
/** |
1622 |
|
* Returns a string identifying this pool, as well as its state, |
1623 |
|
* including indications of run state, parallelism level, and |
1624 |
|
* worker and task counts. |
1635 |
|
int pc = parallelism; |
1636 |
|
int rs = runState; |
1637 |
|
int ac = rs & ACTIVE_COUNT_MASK; |
1638 |
+ |
// int pk = collectParkCount(); |
1639 |
|
return super.toString() + |
1640 |
|
"[" + runLevelToString(rs) + |
1641 |
|
", parallelism = " + pc + |
1645 |
|
", steals = " + st + |
1646 |
|
", tasks = " + qt + |
1647 |
|
", submissions = " + qs + |
1648 |
+ |
// ", parks = " + pk + |
1649 |
|
"]"; |
1650 |
|
} |
1651 |
|
|
1741 |
|
*/ |
1742 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1743 |
|
throws InterruptedException { |
1744 |
< |
return terminationLatch.await(timeout, unit); |
1744 |
> |
try { |
1745 |
> |
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1746 |
> |
} catch(TimeoutException ex) { |
1747 |
> |
return false; |
1748 |
> |
} |
1749 |
|
} |
1750 |
|
|
1751 |
|
/** |
1797 |
|
* Blocks in accord with the given blocker. If the current thread |
1798 |
|
* is a {@link ForkJoinWorkerThread}, this method possibly |
1799 |
|
* arranges for a spare thread to be activated if necessary to |
1800 |
< |
* ensure parallelism while the current thread is blocked. |
1877 |
< |
* |
1878 |
< |
* <p>If {@code maintainParallelism} is {@code true} and the pool |
1879 |
< |
* supports it ({@link #getMaintainsParallelism}), this method |
1880 |
< |
* attempts to maintain the pool's nominal parallelism. Otherwise |
1881 |
< |
* it activates a thread only if necessary to avoid complete |
1882 |
< |
* starvation. This option may be preferable when blockages use |
1883 |
< |
* timeouts, or are almost always brief. |
1800 |
> |
* ensure sufficient parallelism while the current thread is blocked. |
1801 |
|
* |
1802 |
|
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
1803 |
|
* behaviorally equivalent to |
1811 |
|
* first be expanded to ensure parallelism, and later adjusted. |
1812 |
|
* |
1813 |
|
* @param blocker the blocker |
1897 |
– |
* @param maintainParallelism if {@code true} and supported by |
1898 |
– |
* this pool, attempt to maintain the pool's nominal parallelism; |
1899 |
– |
* otherwise activate a thread only if necessary to avoid |
1900 |
– |
* complete starvation. |
1814 |
|
* @throws InterruptedException if blocker.block did so |
1815 |
|
*/ |
1816 |
< |
public static void managedBlock(ManagedBlocker blocker, |
1904 |
< |
boolean maintainParallelism) |
1816 |
> |
public static void managedBlock(ManagedBlocker blocker) |
1817 |
|
throws InterruptedException { |
1818 |
|
Thread t = Thread.currentThread(); |
1819 |
|
if (t instanceof ForkJoinWorkerThread) |
1820 |
< |
((ForkJoinWorkerThread) t).pool. |
1821 |
< |
doBlock(blocker, maintainParallelism); |
1822 |
< |
else |
1823 |
< |
awaitBlocker(blocker); |
1912 |
< |
} |
1913 |
< |
|
1914 |
< |
/** |
1915 |
< |
* Performs Non-FJ blocking |
1916 |
< |
*/ |
1917 |
< |
private static void awaitBlocker(ManagedBlocker blocker) |
1918 |
< |
throws InterruptedException { |
1919 |
< |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1820 |
> |
((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker); |
1821 |
> |
else { |
1822 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1823 |
> |
} |
1824 |
|
} |
1825 |
|
|
1826 |
|
// AbstractExecutorService overrides. These rely on undocumented |
1849 |
|
private static final long stealCountOffset = |
1850 |
|
objectFieldOffset("stealCount",ForkJoinPool.class); |
1851 |
|
|
1948 |
– |
|
1852 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
1853 |
|
try { |
1854 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |