5 |
|
*/ |
6 |
|
|
7 |
|
package jsr166y; |
8 |
< |
import java.util.*; |
8 |
> |
|
9 |
|
import java.util.concurrent.*; |
10 |
< |
import java.util.concurrent.locks.*; |
11 |
< |
import java.util.concurrent.atomic.*; |
12 |
< |
import sun.misc.Unsafe; |
13 |
< |
import java.lang.reflect.*; |
10 |
> |
|
11 |
> |
import java.util.ArrayList; |
12 |
> |
import java.util.Arrays; |
13 |
> |
import java.util.Collection; |
14 |
> |
import java.util.Collections; |
15 |
> |
import java.util.List; |
16 |
> |
import java.util.concurrent.locks.LockSupport; |
17 |
> |
import java.util.concurrent.locks.ReentrantLock; |
18 |
> |
import java.util.concurrent.atomic.AtomicInteger; |
19 |
> |
import java.util.concurrent.CountDownLatch; |
20 |
|
|
21 |
|
/** |
22 |
< |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
23 |
< |
* ForkJoinPool provides the entry point for submissions from |
24 |
< |
* non-ForkJoinTasks, as well as management and monitoring operations. |
25 |
< |
* Normally a single ForkJoinPool is used for a large number of |
20 |
< |
* submitted tasks. Otherwise, use would not usually outweigh the |
21 |
< |
* construction and bookkeeping overhead of creating a large set of |
22 |
< |
* threads. |
22 |
> |
* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
23 |
> |
* A {@code ForkJoinPool} provides the entry point for submissions |
24 |
> |
* from non-{@code ForkJoinTask} clients, as well as management and |
25 |
> |
* monitoring operations. |
26 |
|
* |
27 |
< |
* <p>ForkJoinPools differ from other kinds of Executors mainly in |
28 |
< |
* that they provide <em>work-stealing</em>: all threads in the pool |
29 |
< |
* attempt to find and execute subtasks created by other active tasks |
30 |
< |
* (eventually blocking if none exist). This makes them efficient when |
31 |
< |
* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
32 |
< |
* as the mixed execution of some plain Runnable- or Callable- based |
33 |
< |
* activities along with ForkJoinTasks. When setting |
34 |
< |
* <tt>setAsyncMode</tt>, a ForkJoinPools may also be appropriate for |
35 |
< |
* use with fine-grained tasks that are never joined. Otherwise, other |
33 |
< |
* ExecutorService implementations are typically more appropriate |
34 |
< |
* choices. |
27 |
> |
* <p>A {@code ForkJoinPool} differs from other kinds of {@link |
28 |
> |
* ExecutorService} mainly by virtue of employing |
29 |
> |
* <em>work-stealing</em>: all threads in the pool attempt to find and |
30 |
> |
* execute subtasks created by other active tasks (eventually blocking |
31 |
> |
* waiting for work if none exist). This enables efficient processing |
32 |
> |
* when most tasks spawn other subtasks (as do most {@code |
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 |
|
* |
37 |
< |
* <p>A ForkJoinPool may be constructed with a given parallelism level |
38 |
< |
* (target pool size), which it attempts to maintain by dynamically |
39 |
< |
* adding, suspending, or resuming threads, even if some tasks are |
40 |
< |
* waiting to join others. However, no such adjustments are performed |
41 |
< |
* in the face of blocked IO or other unmanaged synchronization. The |
42 |
< |
* nested <code>ManagedBlocker</code> interface enables extension of |
43 |
< |
* the kinds of synchronization accommodated. The target parallelism |
44 |
< |
* level may also be changed dynamically (<code>setParallelism</code>) |
45 |
< |
* and thread construction can be limited using methods |
45 |
< |
* <code>setMaximumPoolSize</code> and/or |
46 |
< |
* <code>setMaintainsParallelism</code>. |
37 |
> |
* <p>A {@code ForkJoinPool} is constructed with a given target |
38 |
> |
* parallelism level; by default, equal to the number of available |
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 |
|
* <p>In addition to execution and lifecycle control methods, this |
48 |
|
* class provides status check methods (for example |
49 |
< |
* <code>getStealCount</code>) that are intended to aid in developing, |
49 |
> |
* {@link #getStealCount}) that are intended to aid in developing, |
50 |
|
* tuning, and monitoring fork/join applications. Also, method |
51 |
< |
* <code>toString</code> returns indications of pool state in a |
51 |
> |
* {@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 |
+ |
* main task execution methods summarized in the follwoing |
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 |
+ |
* |
65 |
+ |
* <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 |
+ |
* </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 |
91 |
+ |
* bookkeeping overhead of creating a large set of threads. For |
92 |
+ |
* example, a common pool could be used for the {@code SortTasks} |
93 |
+ |
* illustrated in {@link RecursiveAction}. Because {@code |
94 |
+ |
* ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon |
95 |
+ |
* daemon} mode, there is typically no need to explicitly {@link |
96 |
+ |
* #shutdown} such a pool upon program exit. |
97 |
+ |
* |
98 |
+ |
* <pre> |
99 |
+ |
* static final ForkJoinPool mainPool = new ForkJoinPool(); |
100 |
+ |
* ... |
101 |
+ |
* public void sort(long[] array) { |
102 |
+ |
* mainPool.invoke(new SortTask(array, 0, array.length)); |
103 |
+ |
* } |
104 |
+ |
* </pre> |
105 |
+ |
* |
106 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
107 |
|
* maximum number of running threads to 32767. Attempts to create |
108 |
< |
* pools with greater than the maximum result in |
109 |
< |
* IllegalArgumentExceptions. |
108 |
> |
* pools with greater than the maximum number result in |
109 |
> |
* {@code IllegalArgumentException}. |
110 |
> |
* |
111 |
> |
* <p>This implementation rejects submitted tasks (that is, by throwing |
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 |
117 |
|
*/ |
118 |
|
public class ForkJoinPool extends AbstractExecutorService { |
119 |
|
|
120 |
|
/* |
121 |
< |
* See the extended comments interspersed below for design, |
122 |
< |
* rationale, and walkthroughs. |
123 |
< |
*/ |
124 |
< |
|
125 |
< |
/** Mask for packing and unpacking shorts */ |
126 |
< |
private static final int shortMask = 0xffff; |
127 |
< |
|
128 |
< |
/** Max pool size -- must be a power of two minus 1 */ |
129 |
< |
private static final int MAX_THREADS = 0x7FFF; |
130 |
< |
|
131 |
< |
/** |
132 |
< |
* Factory for creating new ForkJoinWorkerThreads. A |
133 |
< |
* ForkJoinWorkerThreadFactory must be defined and used for |
134 |
< |
* ForkJoinWorkerThread subclasses that extend base functionality |
135 |
< |
* or initialize threads with different contexts. |
121 |
> |
* Implementation Overview |
122 |
> |
* |
123 |
> |
* This class provides the central bookkeeping and control for a |
124 |
> |
* set of worker threads: Submissions from non-FJ threads enter |
125 |
> |
* into a submission queue. Workers take these tasks and typically |
126 |
> |
* split them into subtasks that may be stolen by other workers. |
127 |
> |
* The main work-stealing mechanics implemented in class |
128 |
> |
* ForkJoinWorkerThread give first priority to processing tasks |
129 |
> |
* from their own queues (LIFO or FIFO, depending on mode), then |
130 |
> |
* to randomized FIFO steals of tasks in other worker queues, and |
131 |
> |
* lastly to new submissions. These mechanics do not consider |
132 |
> |
* affinities, loads, cache localities, etc, so rarely provide the |
133 |
> |
* best possible performance on a given machine, but portably |
134 |
> |
* provide good throughput by averaging over these factors. |
135 |
> |
* (Further, even if we did try to use such information, we do not |
136 |
> |
* usually have a basis for exploiting it. For example, some sets |
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 arrange tactics for |
142 |
> |
* when one worker is waiting to join a task stolen (or always |
143 |
> |
* held by) another. Becauae we are multiplexing many tasks on to |
144 |
> |
* a pool of workers, we can't just let them block (as in |
145 |
> |
* Thread.join). We also cannot just reassign the joiner's |
146 |
> |
* run-time stack with another and replace it later, which would |
147 |
> |
* be a form of "continuation", that even if possible is not |
148 |
> |
* necessarily a good idea. Given that the creation costs of most |
149 |
> |
* threads on most systems mainly surrounds setting up runtime |
150 |
> |
* stacks, thread creation and switching is usually not much more |
151 |
> |
* expensive than stack creation and switching, and is more |
152 |
> |
* flexible). Instead we combine two tactics: |
153 |
> |
* |
154 |
> |
* 1. 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 |
> |
* |
159 |
> |
* 2. Unless there are already enough live threads, creating or |
160 |
> |
* or re-activating a spare thread to compensate for the |
161 |
> |
* (blocked) joiner until it unblocks. Spares then suspend |
162 |
> |
* at their next opportunity or eventually die if unused for |
163 |
> |
* too long. See below and the internal documentation |
164 |
> |
* for tryAwaitJoin for more details about compensation |
165 |
> |
* 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 option (1) so uses a |
177 |
> |
* special version of (2) 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 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 |
198 |
> |
* structure to support index-based random steals by workers. |
199 |
> |
* Updates to the array recording new workers and unrecording |
200 |
> |
* terminated ones are protected from each other by a lock |
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 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 |
> |
* 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. 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 |
226 |
> |
* those in other Executor implementations, as well as a count of |
227 |
> |
* "active" workers -- those that are, or soon will be, or |
228 |
> |
* recently were executing tasks. The runLevel and active count |
229 |
> |
* are packed together in order to correctly trigger shutdown and |
230 |
> |
* termination. Without care, active counts can be subject to very |
231 |
> |
* high contention. We substantially reduce this contention by |
232 |
> |
* relaxing update rules. A worker must claim active status |
233 |
> |
* prospectively, by activating if it sees that a submitted or |
234 |
> |
* stealable task exists (it may find after activating that the |
235 |
> |
* task no longer exists). It stays active while processing this |
236 |
> |
* task (if it exists) and any other local subtasks it produces, |
237 |
> |
* until it cannot find any other tasks. It then tries |
238 |
> |
* inactivating (see method preStep), but upon update contention |
239 |
> |
* instead scans for more tasks, later retrying inactivation if it |
240 |
> |
* doesn't find any. |
241 |
> |
* |
242 |
> |
* 4. Managing idle workers waiting for tasks. We cannot let |
243 |
> |
* workers spin indefinitely scanning for tasks when none are |
244 |
> |
* available. On the other hand, we must quickly prod them into |
245 |
> |
* action when new tasks are submitted or generated. We |
246 |
> |
* park/unpark these idle workers using an event-count scheme. |
247 |
> |
* Field eventCount is incremented upon events that may enable |
248 |
> |
* workers that previously could not find a task to now find one: |
249 |
> |
* Submission of a new task to the pool, or another worker pushing |
250 |
> |
* a task onto a previously empty queue. (We also use this |
251 |
> |
* mechanism for termination and reconfiguration actions that |
252 |
> |
* require wakeups of idle workers). Each worker maintains its |
253 |
> |
* last known event count, and blocks when a scan for work did not |
254 |
> |
* find a task AND its lastEventCount matches the current |
255 |
> |
* eventCount. Waiting idle workers are recorded in a variant of |
256 |
> |
* Treiber stack headed by field eventWaiters which, when nonzero, |
257 |
> |
* encodes the thread index and count awaited for by the worker |
258 |
> |
* thread most recently calling eventSync. This thread in turn has |
259 |
> |
* a record (field nextEventWaiter) for the next waiting worker. |
260 |
> |
* In addition to allowing simpler decisions about need for |
261 |
> |
* wakeup, the event count bits in eventWaiters serve the role of |
262 |
> |
* tags to avoid ABA errors in Treiber stacks. To reduce delays |
263 |
> |
* in task diffusion, workers not otherwise occupied may invoke |
264 |
> |
* method releaseWaiters, that removes and signals (unparks) |
265 |
> |
* workers not waiting on current count. To minimize task |
266 |
> |
* production stalls associate with signalling, any worker pushing |
267 |
> |
* a task on an empty queue invokes the weaker method signalWork, |
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 |
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 |
275 |
> |
* when their only purpose is to enable workers to scan for work. |
276 |
> |
* |
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. 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 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 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 |
329 |
> |
* ForkJoinTask. For example, direct access to "workers" array by |
330 |
> |
* workers, and direct access to ForkJoinTask.status by both |
331 |
> |
* ForkJoinPool and ForkJoinWorkerThread. There is little point |
332 |
> |
* trying to reduce this, since any associated future changes in |
333 |
> |
* representations will need to be accompanied by algorithmic |
334 |
> |
* changes anyway. |
335 |
> |
* |
336 |
> |
* Style notes: There are lots of inline assignments (of form |
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 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) |
346 |
> |
* (3) internal control methods (4) callbacks and other support |
347 |
> |
* for ForkJoinTask and ForkJoinWorkerThread classes, (5) exported |
348 |
> |
* methods (plus a few little helpers). |
349 |
> |
*/ |
350 |
> |
|
351 |
> |
/** |
352 |
> |
* Factory for creating new {@link ForkJoinWorkerThread}s. |
353 |
> |
* A {@code ForkJoinWorkerThreadFactory} must be defined and used |
354 |
> |
* for {@code ForkJoinWorkerThread} subclasses that extend base |
355 |
> |
* functionality or initialize threads with different contexts. |
356 |
|
*/ |
357 |
|
public static interface ForkJoinWorkerThreadFactory { |
358 |
|
/** |
359 |
|
* Returns a new worker thread operating in the given pool. |
360 |
|
* |
361 |
|
* @param pool the pool this thread works in |
362 |
< |
* @throws NullPointerException if pool is null; |
362 |
> |
* @throws NullPointerException if the pool is null |
363 |
|
*/ |
364 |
|
public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
365 |
|
} |
366 |
|
|
367 |
|
/** |
368 |
< |
* Default ForkJoinWorkerThreadFactory implementation, creates a |
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 |
< |
try { |
97 |
< |
return new ForkJoinWorkerThread(pool); |
98 |
< |
} catch (OutOfMemoryError oom) { |
99 |
< |
return null; |
100 |
< |
} |
374 |
> |
return new ForkJoinWorkerThread(pool); |
375 |
|
} |
376 |
|
} |
377 |
|
|
407 |
|
new AtomicInteger(); |
408 |
|
|
409 |
|
/** |
410 |
< |
* Array holding all worker threads in the pool. Initialized upon |
411 |
< |
* first use. Array size must be a power of two. Updates and |
138 |
< |
* replacements are protected by workerLock, but it is always kept |
139 |
< |
* in a consistent enough state to be randomly accessed without |
140 |
< |
* locking by workers performing work-stealing. |
410 |
> |
* Absolute bound for parallelism level. Twice this number must |
411 |
> |
* fit into a 16bit field to enable word-packing for some counts. |
412 |
|
*/ |
413 |
< |
volatile ForkJoinWorkerThread[] workers; |
413 |
> |
private static final int MAX_THREADS = 0x7fff; |
414 |
|
|
415 |
|
/** |
416 |
< |
* Lock protecting access to workers. |
416 |
> |
* Array holding all worker threads in the pool. Array size must |
417 |
> |
* be a power of two. Updates and replacements are protected by |
418 |
> |
* workerLock, but the array is always kept in a consistent enough |
419 |
> |
* state to be randomly accessed without locking by workers |
420 |
> |
* performing work-stealing, as well as other traversal-based |
421 |
> |
* methods in this class. All readers must tolerate that some |
422 |
> |
* array slots may be null. |
423 |
|
*/ |
424 |
< |
private final ReentrantLock workerLock; |
424 |
> |
volatile ForkJoinWorkerThread[] workers; |
425 |
|
|
426 |
|
/** |
427 |
< |
* Condition for awaitTermination. |
427 |
> |
* Queue for external submissions. |
428 |
|
*/ |
429 |
< |
private final Condition termination; |
429 |
> |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
430 |
|
|
431 |
|
/** |
432 |
< |
* The uncaught exception handler used when any worker |
156 |
< |
* abrupty terminates |
432 |
> |
* Lock protecting updates to workers array. |
433 |
|
*/ |
434 |
< |
private Thread.UncaughtExceptionHandler ueh; |
434 |
> |
private final ReentrantLock workerLock; |
435 |
|
|
436 |
|
/** |
437 |
< |
* Creation factory for worker threads. |
437 |
> |
* Latch released upon termination. |
438 |
|
*/ |
439 |
< |
private final ForkJoinWorkerThreadFactory factory; |
439 |
> |
private final Phaser termination; |
440 |
|
|
441 |
|
/** |
442 |
< |
* Head of stack of threads that were created to maintain |
167 |
< |
* parallelism when other threads blocked, but have since |
168 |
< |
* suspended when the parallelism level rose. |
442 |
> |
* Creation factory for worker threads. |
443 |
|
*/ |
444 |
< |
private volatile WaitQueueNode spareStack; |
444 |
> |
private final ForkJoinWorkerThreadFactory factory; |
445 |
|
|
446 |
|
/** |
447 |
|
* Sum of per-thread steal counts, updated only when threads are |
448 |
|
* idle or terminating. |
449 |
|
*/ |
450 |
< |
private final AtomicLong stealCount; |
450 |
> |
private volatile long stealCount; |
451 |
|
|
452 |
|
/** |
453 |
< |
* Queue for external submissions. |
453 |
> |
* Encoded record of top of treiber stack of threads waiting for |
454 |
> |
* events. The top 32 bits contain the count being waited for. The |
455 |
> |
* bottom word contains one plus the pool index of waiting worker |
456 |
> |
* thread. |
457 |
|
*/ |
458 |
< |
private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
458 |
> |
private volatile long eventWaiters; |
459 |
> |
|
460 |
> |
private static final int EVENT_COUNT_SHIFT = 32; |
461 |
> |
private static final long WAITER_ID_MASK = (1L << EVENT_COUNT_SHIFT)-1L; |
462 |
|
|
463 |
|
/** |
464 |
< |
* Head of Treiber stack for barrier sync. See below for explanation |
464 |
> |
* A counter for events that may wake up worker threads: |
465 |
> |
* - Submission of a new task to the pool |
466 |
> |
* - A worker pushing a task on an empty queue |
467 |
> |
* - termination and reconfiguration |
468 |
|
*/ |
469 |
< |
private volatile WaitQueueNode syncStack; |
469 |
> |
private volatile int eventCount; |
470 |
|
|
471 |
|
/** |
472 |
< |
* The count for event barrier |
473 |
< |
*/ |
474 |
< |
private volatile long eventCount; |
472 |
> |
* Lifecycle control. The low word contains the number of workers |
473 |
> |
* that are (probably) executing tasks. This value is atomically |
474 |
> |
* incremented before a worker gets a task to run, and decremented |
475 |
> |
* when worker has no tasks and cannot find any. Bits 16-18 |
476 |
> |
* contain runLevel value. When all are zero, the pool is |
477 |
> |
* running. Level transitions are monotonic (running -> shutdown |
478 |
> |
* -> terminating -> terminated) so each transition adds a bit. |
479 |
> |
* These are bundled together to ensure consistent read for |
480 |
> |
* termination checks (i.e., that runLevel is at least SHUTDOWN |
481 |
> |
* and active threads is zero). |
482 |
> |
*/ |
483 |
> |
private volatile int runState; |
484 |
> |
|
485 |
> |
// Note: The order among run level values matters. |
486 |
> |
private static final int RUNLEVEL_SHIFT = 16; |
487 |
> |
private static final int SHUTDOWN = 1 << RUNLEVEL_SHIFT; |
488 |
> |
private static final int TERMINATING = 1 << (RUNLEVEL_SHIFT + 1); |
489 |
> |
private static final int TERMINATED = 1 << (RUNLEVEL_SHIFT + 2); |
490 |
> |
private static final int ACTIVE_COUNT_MASK = (1 << RUNLEVEL_SHIFT) - 1; |
491 |
> |
private static final int ONE_ACTIVE = 1; // active update delta |
492 |
|
|
493 |
|
/** |
494 |
< |
* Pool number, just for assigning useful names to worker threads |
494 |
> |
* Holds number of total (i.e., created and not yet terminated) |
495 |
> |
* and running (i.e., not blocked on joins or other managed sync) |
496 |
> |
* threads, packed together to ensure consistent snapshot when |
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 |
501 |
> |
* configuration parameters. |
502 |
|
*/ |
503 |
< |
private final int poolNumber; |
503 |
> |
private volatile int workerCounts; |
504 |
> |
|
505 |
> |
private static final int TOTAL_COUNT_SHIFT = 16; |
506 |
> |
private static final int RUNNING_COUNT_MASK = (1 << TOTAL_COUNT_SHIFT) - 1; |
507 |
> |
private static final int ONE_RUNNING = 1; |
508 |
> |
private static final int ONE_TOTAL = 1 << TOTAL_COUNT_SHIFT; |
509 |
|
|
510 |
|
/** |
511 |
< |
* The maximum allowed pool size |
511 |
> |
* The target parallelism level. |
512 |
> |
* Accessed directly by ForkJoinWorkerThreads. |
513 |
|
*/ |
514 |
< |
private volatile int maxPoolSize; |
514 |
> |
final int parallelism; |
515 |
|
|
516 |
|
/** |
517 |
< |
* The desired parallelism level, updated only under workerLock. |
517 |
> |
* True if use local fifo, not default lifo, for local polling |
518 |
> |
* Read by, and replicated by ForkJoinWorkerThreads |
519 |
|
*/ |
520 |
< |
private volatile int parallelism; |
520 |
> |
final boolean locallyFifo; |
521 |
|
|
522 |
|
/** |
523 |
< |
* True if use local fifo, not default lifo, for local polling |
523 |
> |
* The uncaught exception handler used when any worker abruptly |
524 |
> |
* terminates. |
525 |
|
*/ |
526 |
< |
private volatile boolean locallyFifo; |
526 |
> |
private final Thread.UncaughtExceptionHandler ueh; |
527 |
|
|
528 |
|
/** |
529 |
< |
* Holds number of total (i.e., created and not yet terminated) |
215 |
< |
* and running (i.e., not blocked on joins or other managed sync) |
216 |
< |
* threads, packed into one int to ensure consistent snapshot when |
217 |
< |
* making decisions about creating and suspending spare |
218 |
< |
* threads. Updated only by CAS. Note: CASes in |
219 |
< |
* updateRunningCount and preJoin assume that running active count |
220 |
< |
* is in low word, so need to be modified if this changes |
529 |
> |
* Pool number, just for assigning useful names to worker threads |
530 |
|
*/ |
531 |
< |
private volatile int workerCounts; |
531 |
> |
private final int poolNumber; |
532 |
|
|
533 |
< |
private static int totalCountOf(int s) { return s >>> 16; } |
534 |
< |
private static int runningCountOf(int s) { return s & shortMask; } |
226 |
< |
private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
533 |
> |
// Utilities for CASing fields. Note that several of these |
534 |
> |
// are manually inlined by callers |
535 |
|
|
536 |
|
/** |
537 |
< |
* Add delta (which may be negative) to running count. This must |
230 |
< |
* be called before (with negative arg) and after (with positive) |
231 |
< |
* any managed synchronization (i.e., mainly, joins) |
232 |
< |
* @param delta the number to add |
537 |
> |
* Increments running count. Also used by ForkJoinTask. |
538 |
|
*/ |
539 |
< |
final void updateRunningCount(int delta) { |
540 |
< |
int s; |
541 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + delta)); |
539 |
> |
final void incrementRunningCount() { |
540 |
> |
int c; |
541 |
> |
do {} while (!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
542 |
> |
c = workerCounts, |
543 |
> |
c + ONE_RUNNING)); |
544 |
|
} |
545 |
|
|
546 |
|
/** |
547 |
< |
* Add delta (which may be negative) to both total and running |
241 |
< |
* count. This must be called upon creation and termination of |
242 |
< |
* worker threads. |
243 |
< |
* @param delta the number to add |
547 |
> |
* Tries to decrement running count unless already zero |
548 |
|
*/ |
549 |
< |
private void updateWorkerCount(int delta) { |
550 |
< |
int d = delta + (delta << 16); // add to both lo and hi parts |
551 |
< |
int s; |
552 |
< |
do;while (!casWorkerCounts(s = workerCounts, s + d)); |
549 |
> |
final boolean tryDecrementRunningCount() { |
550 |
> |
int wc = workerCounts; |
551 |
> |
if ((wc & RUNNING_COUNT_MASK) == 0) |
552 |
> |
return false; |
553 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
554 |
> |
wc, wc - ONE_RUNNING); |
555 |
|
} |
556 |
|
|
557 |
|
/** |
558 |
< |
* Lifecycle control. High word contains runState, low word |
253 |
< |
* contains the number of workers that are (probably) executing |
254 |
< |
* tasks. This value is atomically incremented before a worker |
255 |
< |
* gets a task to run, and decremented when worker has no tasks |
256 |
< |
* and cannot find any. These two fields are bundled together to |
257 |
< |
* support correct termination triggering. Note: activeCount |
258 |
< |
* CAS'es cheat by assuming active count is in low word, so need |
259 |
< |
* to be modified if this changes |
558 |
> |
* Tries to increment running count |
559 |
|
*/ |
560 |
< |
private volatile int runControl; |
561 |
< |
|
562 |
< |
// RunState values. Order among values matters |
563 |
< |
private static final int RUNNING = 0; |
564 |
< |
private static final int SHUTDOWN = 1; |
266 |
< |
private static final int TERMINATING = 2; |
267 |
< |
private static final int TERMINATED = 3; |
268 |
< |
|
269 |
< |
private static int runStateOf(int c) { return c >>> 16; } |
270 |
< |
private static int activeCountOf(int c) { return c & shortMask; } |
271 |
< |
private static int runControlFor(int r, int a) { return (r << 16) + a; } |
560 |
> |
final boolean tryIncrementRunningCount() { |
561 |
> |
int wc; |
562 |
> |
return UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
563 |
> |
wc = workerCounts, wc + ONE_RUNNING); |
564 |
> |
} |
565 |
|
|
566 |
|
/** |
567 |
< |
* Try incrementing active count; fail on contention. Called by |
568 |
< |
* workers before/during executing tasks. |
569 |
< |
* @return true on success; |
567 |
> |
* Tries incrementing active count; fails on contention. |
568 |
> |
* Called by workers before executing tasks. |
569 |
> |
* |
570 |
> |
* @return true on success |
571 |
|
*/ |
572 |
|
final boolean tryIncrementActiveCount() { |
573 |
< |
int c = runControl; |
574 |
< |
return casRunControl(c, c+1); |
573 |
> |
int c; |
574 |
> |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
575 |
> |
c = runState, c + ONE_ACTIVE); |
576 |
|
} |
577 |
|
|
578 |
|
/** |
579 |
< |
* Try decrementing active count; fail on contention. |
580 |
< |
* Possibly trigger termination on success |
286 |
< |
* Called by workers when they can't find tasks. |
287 |
< |
* @return true on success |
579 |
> |
* Tries decrementing active count; fails on contention. |
580 |
> |
* Called when workers cannot find tasks to run. |
581 |
|
*/ |
582 |
|
final boolean tryDecrementActiveCount() { |
583 |
< |
int c = runControl; |
584 |
< |
int nextc = c - 1; |
585 |
< |
if (!casRunControl(c, nextc)) |
293 |
< |
return false; |
294 |
< |
if (canTerminateOnShutdown(nextc)) |
295 |
< |
terminateOnShutdown(); |
296 |
< |
return true; |
583 |
> |
int c; |
584 |
> |
return UNSAFE.compareAndSwapInt(this, runStateOffset, |
585 |
> |
c = runState, c - ONE_ACTIVE); |
586 |
|
} |
587 |
|
|
588 |
|
/** |
589 |
< |
* Return true if argument represents zero active count and |
590 |
< |
* nonzero runstate, which is the triggering condition for |
302 |
< |
* terminating on shutdown. |
589 |
> |
* Advances to at least the given level. Returns true if not |
590 |
> |
* already in at least the given level. |
591 |
|
*/ |
592 |
< |
private static boolean canTerminateOnShutdown(int c) { |
593 |
< |
return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit |
592 |
> |
private boolean advanceRunLevel(int level) { |
593 |
> |
for (;;) { |
594 |
> |
int s = runState; |
595 |
> |
if ((s & level) != 0) |
596 |
> |
return false; |
597 |
> |
if (UNSAFE.compareAndSwapInt(this, runStateOffset, s, s | level)) |
598 |
> |
return true; |
599 |
> |
} |
600 |
|
} |
601 |
|
|
602 |
+ |
// workers array maintenance |
603 |
+ |
|
604 |
|
/** |
605 |
< |
* Transition run state to at least the given state. Return true |
310 |
< |
* if not already at least given state. |
605 |
> |
* Records and returns a workers array index for new worker. |
606 |
|
*/ |
607 |
< |
private boolean transitionRunStateTo(int state) { |
608 |
< |
for (;;) { |
609 |
< |
int c = runControl; |
610 |
< |
if (runStateOf(c) >= state) |
611 |
< |
return false; |
612 |
< |
if (casRunControl(c, runControlFor(state, activeCountOf(c)))) |
613 |
< |
return true; |
607 |
> |
private int recordWorker(ForkJoinWorkerThread w) { |
608 |
> |
// Try using slot totalCount-1. If not available, scan and/or resize |
609 |
> |
int k = (workerCounts >>> TOTAL_COUNT_SHIFT) - 1; |
610 |
> |
final ReentrantLock lock = this.workerLock; |
611 |
> |
lock.lock(); |
612 |
> |
try { |
613 |
> |
ForkJoinWorkerThread[] ws = workers; |
614 |
> |
int nws = ws.length; |
615 |
> |
if (k < 0 || k >= nws || ws[k] != null) { |
616 |
> |
for (k = 0; k < nws && ws[k] != null; ++k) |
617 |
> |
; |
618 |
> |
if (k == nws) |
619 |
> |
ws = Arrays.copyOf(ws, nws << 1); |
620 |
> |
} |
621 |
> |
ws[k] = w; |
622 |
> |
workers = ws; // volatile array write ensures slot visibility |
623 |
> |
} finally { |
624 |
> |
lock.unlock(); |
625 |
|
} |
626 |
+ |
return k; |
627 |
|
} |
628 |
|
|
629 |
|
/** |
630 |
< |
* Controls whether to add spares to maintain parallelism |
630 |
> |
* Nulls out record of worker in workers array |
631 |
|
*/ |
632 |
< |
private volatile boolean maintainsParallelism; |
632 |
> |
private void forgetWorker(ForkJoinWorkerThread w) { |
633 |
> |
int idx = w.poolIndex; |
634 |
> |
// Locking helps method recordWorker avoid unecessary expansion |
635 |
> |
final ReentrantLock lock = this.workerLock; |
636 |
> |
lock.lock(); |
637 |
> |
try { |
638 |
> |
ForkJoinWorkerThread[] ws = workers; |
639 |
> |
if (idx >= 0 && idx < ws.length && ws[idx] == w) // verify |
640 |
> |
ws[idx] = null; |
641 |
> |
} finally { |
642 |
> |
lock.unlock(); |
643 |
> |
} |
644 |
> |
} |
645 |
|
|
646 |
< |
// Constructors |
646 |
> |
// adding and removing workers |
647 |
|
|
648 |
|
/** |
649 |
< |
* Creates a ForkJoinPool with a pool size equal to the number of |
650 |
< |
* processors available on the system and using the default |
651 |
< |
* ForkJoinWorkerThreadFactory, |
652 |
< |
* @throws SecurityException if a security manager exists and |
653 |
< |
* the caller is not permitted to modify threads |
335 |
< |
* because it does not hold {@link |
336 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
649 |
> |
* Tries to create and add new worker. Assumes that worker counts |
650 |
> |
* are already updated to accommodate the worker, so adjusts on |
651 |
> |
* failure. |
652 |
> |
* |
653 |
> |
* @return new worker or null if creation failed |
654 |
|
*/ |
655 |
< |
public ForkJoinPool() { |
656 |
< |
this(Runtime.getRuntime().availableProcessors(), |
657 |
< |
defaultForkJoinWorkerThreadFactory); |
655 |
> |
private ForkJoinWorkerThread addWorker() { |
656 |
> |
ForkJoinWorkerThread w = null; |
657 |
> |
try { |
658 |
> |
w = factory.newThread(this); |
659 |
> |
} finally { // Adjust on either null or exceptional factory return |
660 |
> |
if (w == null) { |
661 |
> |
onWorkerCreationFailure(); |
662 |
> |
return null; |
663 |
> |
} |
664 |
> |
} |
665 |
> |
w.start(recordWorker(w), ueh); |
666 |
> |
return w; |
667 |
|
} |
668 |
|
|
669 |
|
/** |
670 |
< |
* Creates a ForkJoinPool with the indicated parellelism level |
345 |
< |
* threads, and using the default ForkJoinWorkerThreadFactory, |
346 |
< |
* @param parallelism the number of worker threads |
347 |
< |
* @throws IllegalArgumentException if parallelism less than or |
348 |
< |
* equal to zero |
349 |
< |
* @throws SecurityException if a security manager exists and |
350 |
< |
* the caller is not permitted to modify threads |
351 |
< |
* because it does not hold {@link |
352 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
670 |
> |
* Adjusts counts upon failure to create worker |
671 |
|
*/ |
672 |
< |
public ForkJoinPool(int parallelism) { |
673 |
< |
this(parallelism, defaultForkJoinWorkerThreadFactory); |
672 |
> |
private void onWorkerCreationFailure() { |
673 |
> |
for (;;) { |
674 |
> |
int wc = workerCounts; |
675 |
> |
if ((wc >>> TOTAL_COUNT_SHIFT) == 0) |
676 |
> |
Thread.yield(); // 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 |
< |
* Creates a ForkJoinPool with parallelism equal to the number of |
686 |
< |
* processors available on the system and using the given |
687 |
< |
* ForkJoinWorkerThreadFactory, |
688 |
< |
* @param factory the factory for creating new threads |
689 |
< |
* @throws NullPointerException if factory is null |
690 |
< |
* @throws SecurityException if a security manager exists and |
691 |
< |
* the caller is not permitted to modify threads |
692 |
< |
* because it does not hold {@link |
693 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
694 |
< |
*/ |
695 |
< |
public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
696 |
< |
this(Runtime.getRuntime().availableProcessors(), factory); |
685 |
> |
* Creates and/or resumes enough workers to establish target |
686 |
> |
* parallelism, giving up if terminating or addWorker fails |
687 |
> |
* |
688 |
> |
* TODO: recast this to support lazier creation and automated |
689 |
> |
* parallelism maintenance |
690 |
> |
*/ |
691 |
> |
private void ensureEnoughWorkers() { |
692 |
> |
while ((runState & TERMINATING) == 0) { |
693 |
> |
int pc = parallelism; |
694 |
> |
int wc = workerCounts; |
695 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
696 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
697 |
> |
if (tc < pc) { |
698 |
> |
if (UNSAFE.compareAndSwapInt |
699 |
> |
(this, workerCountsOffset, |
700 |
> |
wc, wc + (ONE_RUNNING|ONE_TOTAL)) && |
701 |
> |
addWorker() == null) |
702 |
> |
break; |
703 |
> |
} |
704 |
> |
else if (tc > pc && rc < pc && |
705 |
> |
tc > (runState & ACTIVE_COUNT_MASK)) { |
706 |
> |
ForkJoinWorkerThread spare = null; |
707 |
> |
ForkJoinWorkerThread[] ws = workers; |
708 |
> |
int nws = ws.length; |
709 |
> |
for (int i = 0; i < nws; ++i) { |
710 |
> |
ForkJoinWorkerThread w = ws[i]; |
711 |
> |
if (w != null && w.isSuspended()) { |
712 |
> |
if ((workerCounts & RUNNING_COUNT_MASK) > pc) |
713 |
> |
return; |
714 |
> |
if (w.tryResumeSpare()) |
715 |
> |
incrementRunningCount(); |
716 |
> |
break; |
717 |
> |
} |
718 |
> |
} |
719 |
> |
} |
720 |
> |
else |
721 |
> |
break; |
722 |
> |
} |
723 |
|
} |
724 |
|
|
725 |
|
/** |
726 |
< |
* Creates a ForkJoinPool with the given parallelism and factory. |
726 |
> |
* Final callback from terminating worker. Removes record of |
727 |
> |
* worker from array, and adjusts counts. If pool is shutting |
728 |
> |
* down, tries to complete terminatation, else possibly replaces |
729 |
> |
* the worker. |
730 |
|
* |
731 |
< |
* @param parallelism the targeted number of worker threads |
377 |
< |
* @param factory the factory for creating new threads |
378 |
< |
* @throws IllegalArgumentException if parallelism less than or |
379 |
< |
* equal to zero, or greater than implementation limit. |
380 |
< |
* @throws NullPointerException if factory is null |
381 |
< |
* @throws SecurityException if a security manager exists and |
382 |
< |
* the caller is not permitted to modify threads |
383 |
< |
* because it does not hold {@link |
384 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
731 |
> |
* @param w the worker |
732 |
|
*/ |
733 |
< |
public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
734 |
< |
if (parallelism <= 0 || parallelism > MAX_THREADS) |
735 |
< |
throw new IllegalArgumentException(); |
736 |
< |
if (factory == null) |
737 |
< |
throw new NullPointerException(); |
738 |
< |
checkPermission(); |
739 |
< |
this.factory = factory; |
740 |
< |
this.parallelism = parallelism; |
741 |
< |
this.maxPoolSize = MAX_THREADS; |
742 |
< |
this.maintainsParallelism = true; |
743 |
< |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
744 |
< |
this.workerLock = new ReentrantLock(); |
745 |
< |
this.termination = workerLock.newCondition(); |
746 |
< |
this.stealCount = new AtomicLong(); |
747 |
< |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
748 |
< |
// worker array and workers are lazily constructed |
733 |
> |
final void workerTerminated(ForkJoinWorkerThread w) { |
734 |
> |
if (w.active) { // force inactive |
735 |
> |
w.active = false; |
736 |
> |
do {} while (!tryDecrementActiveCount()); |
737 |
> |
} |
738 |
> |
forgetWorker(w); |
739 |
> |
|
740 |
> |
// Decrement total count, and if was running, running count |
741 |
> |
// Spin (waiting for other updates) if either would be negative |
742 |
> |
int nr = w.isTrimmed() ? 0 : ONE_RUNNING; |
743 |
> |
int unit = ONE_TOTAL + nr; |
744 |
> |
for (;;) { |
745 |
> |
int wc = workerCounts; |
746 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
747 |
> |
if (rc - nr < 0 || (wc >>> TOTAL_COUNT_SHIFT) == 0) |
748 |
> |
Thread.yield(); // back off if waiting for other updates |
749 |
> |
else if (UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
750 |
> |
wc, wc - unit)) |
751 |
> |
break; |
752 |
> |
} |
753 |
> |
|
754 |
> |
accumulateStealCount(w); // collect final count |
755 |
> |
if (!tryTerminate(false)) |
756 |
> |
ensureEnoughWorkers(); |
757 |
|
} |
758 |
|
|
759 |
+ |
// Waiting for and signalling events |
760 |
+ |
|
761 |
|
/** |
762 |
< |
* Create new worker using factory. |
763 |
< |
* @param index the index to assign worker |
764 |
< |
* @return new worker, or null of factory failed |
765 |
< |
*/ |
766 |
< |
private ForkJoinWorkerThread createWorker(int index) { |
767 |
< |
Thread.UncaughtExceptionHandler h = ueh; |
768 |
< |
ForkJoinWorkerThread w = factory.newThread(this); |
769 |
< |
if (w != null) { |
770 |
< |
w.poolIndex = index; |
771 |
< |
w.setDaemon(true); |
772 |
< |
w.setAsyncMode(locallyFifo); |
773 |
< |
w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index); |
774 |
< |
if (h != null) |
775 |
< |
w.setUncaughtExceptionHandler(h); |
762 |
> |
* Releases workers blocked on a count not equal to current count. |
763 |
> |
* @return true if any released |
764 |
> |
*/ |
765 |
> |
private void releaseWaiters() { |
766 |
> |
long top; |
767 |
> |
while ((top = eventWaiters) != 0L) { |
768 |
> |
ForkJoinWorkerThread[] ws = workers; |
769 |
> |
int n = ws.length; |
770 |
> |
for (;;) { |
771 |
> |
int i = ((int)(top & WAITER_ID_MASK)) - 1; |
772 |
> |
if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == eventCount) |
773 |
> |
return; |
774 |
> |
ForkJoinWorkerThread w; |
775 |
> |
if (i < n && (w = ws[i]) != null && |
776 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
777 |
> |
top, w.nextWaiter)) { |
778 |
> |
LockSupport.unpark(w); |
779 |
> |
top = eventWaiters; |
780 |
> |
} |
781 |
> |
else |
782 |
> |
break; // possibly stale; reread |
783 |
> |
} |
784 |
|
} |
420 |
– |
return w; |
785 |
|
} |
786 |
|
|
787 |
|
/** |
788 |
< |
* Return a good size for worker array given pool size. |
789 |
< |
* Currently requires size to be a power of two. |
788 |
> |
* Ensures eventCount on exit is different (mod 2^32) than on |
789 |
> |
* entry and wakes up all waiters |
790 |
|
*/ |
791 |
< |
private static int arraySizeFor(int ps) { |
792 |
< |
return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1))); |
791 |
> |
private void signalEvent() { |
792 |
> |
int c; |
793 |
> |
do {} while (!UNSAFE.compareAndSwapInt(this, eventCountOffset, |
794 |
> |
c = eventCount, c+1)); |
795 |
> |
releaseWaiters(); |
796 |
|
} |
797 |
|
|
798 |
|
/** |
799 |
< |
* Create or resize array if necessary to hold newLength. |
800 |
< |
* Call only under exclusion |
434 |
< |
* @return the array |
799 |
> |
* Advances eventCount and releases waiters until interference by |
800 |
> |
* other releasing threads is detected. |
801 |
|
*/ |
802 |
< |
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
803 |
< |
ForkJoinWorkerThread[] ws = workers; |
804 |
< |
if (ws == null) |
805 |
< |
return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)]; |
806 |
< |
else if (newLength > ws.length) |
807 |
< |
return workers = Arrays.copyOf(ws, arraySizeFor(newLength)); |
808 |
< |
else |
809 |
< |
return ws; |
802 |
> |
final void signalWork() { |
803 |
> |
int c; |
804 |
> |
UNSAFE.compareAndSwapInt(this, eventCountOffset, c=eventCount, c+1); |
805 |
> |
long top; |
806 |
> |
while ((top = eventWaiters) != 0L) { |
807 |
> |
int ec = eventCount; |
808 |
> |
ForkJoinWorkerThread[] ws = workers; |
809 |
> |
int n = ws.length; |
810 |
> |
for (;;) { |
811 |
> |
int i = ((int)(top & WAITER_ID_MASK)) - 1; |
812 |
> |
if (i < 0 || (int)(top >>> EVENT_COUNT_SHIFT) == ec) |
813 |
> |
return; |
814 |
> |
ForkJoinWorkerThread w; |
815 |
> |
if (i < n && (w = ws[i]) != null && |
816 |
> |
UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
817 |
> |
top, top = w.nextWaiter)) { |
818 |
> |
LockSupport.unpark(w); |
819 |
> |
if (top != eventWaiters) // let someone else take over |
820 |
> |
return; |
821 |
> |
} |
822 |
> |
else |
823 |
> |
break; // possibly stale; reread |
824 |
> |
} |
825 |
> |
} |
826 |
|
} |
827 |
|
|
828 |
|
/** |
829 |
< |
* Try to shrink workers into smaller array after one or more terminate |
829 |
> |
* If worker is inactive, blocks until terminating or event count |
830 |
> |
* advances from last value held by worker; in any case helps |
831 |
> |
* release others. |
832 |
> |
* |
833 |
> |
* @param w the calling worker thread |
834 |
> |
* @param retries the number of scans by caller failing to find work |
835 |
> |
* @return false if now too many threads running |
836 |
|
*/ |
837 |
< |
private void tryShrinkWorkerArray() { |
838 |
< |
ForkJoinWorkerThread[] ws = workers; |
839 |
< |
if (ws != null) { |
840 |
< |
int len = ws.length; |
841 |
< |
int last = len - 1; |
842 |
< |
while (last >= 0 && ws[last] == null) |
843 |
< |
--last; |
844 |
< |
int newLength = arraySizeFor(last+1); |
845 |
< |
if (newLength < len) |
846 |
< |
workers = Arrays.copyOf(ws, newLength); |
837 |
> |
private boolean eventSync(ForkJoinWorkerThread w, int retries) { |
838 |
> |
int wec = w.lastEventCount; |
839 |
> |
if (retries > 1) { // can only block after 2nd miss |
840 |
> |
long nextTop = (((long)wec << EVENT_COUNT_SHIFT) | |
841 |
> |
((long)(w.poolIndex + 1))); |
842 |
> |
long top; |
843 |
> |
while ((runState < SHUTDOWN || !tryTerminate(false)) && |
844 |
> |
(((int)(top = eventWaiters) & WAITER_ID_MASK) == 0 || |
845 |
> |
(int)(top >>> EVENT_COUNT_SHIFT) == wec) && |
846 |
> |
eventCount == wec) { |
847 |
> |
if (UNSAFE.compareAndSwapLong(this, eventWaitersOffset, |
848 |
> |
w.nextWaiter = top, nextTop)) { |
849 |
> |
accumulateStealCount(w); // transfer steals while idle |
850 |
> |
Thread.interrupted(); // clear/ignore interrupt |
851 |
> |
while (eventCount == wec) |
852 |
> |
w.doPark(); |
853 |
> |
break; |
854 |
> |
} |
855 |
> |
} |
856 |
> |
wec = eventCount; |
857 |
|
} |
858 |
+ |
releaseWaiters(); |
859 |
+ |
int wc = workerCounts; |
860 |
+ |
if ((wc & RUNNING_COUNT_MASK) <= parallelism) { |
861 |
+ |
w.lastEventCount = wec; |
862 |
+ |
return true; |
863 |
+ |
} |
864 |
+ |
if (wec != w.lastEventCount) // back up if may re-wait |
865 |
+ |
w.lastEventCount = wec - (wc >>> TOTAL_COUNT_SHIFT); |
866 |
+ |
return false; |
867 |
|
} |
868 |
|
|
869 |
|
/** |
870 |
< |
* Initialize workers if necessary |
870 |
> |
* Callback from workers invoked upon each top-level action (i.e., |
871 |
> |
* stealing a task or taking a submission and running |
872 |
> |
* it). Performs one or both of the following: |
873 |
> |
* |
874 |
> |
* * If the worker cannot find work, updates its active status to |
875 |
> |
* inactive and updates activeCount unless there is contention, in |
876 |
> |
* which case it may try again (either in this or a subsequent |
877 |
> |
* call). Additionally, awaits the next task event and/or helps |
878 |
> |
* wake up other releasable waiters. |
879 |
> |
* |
880 |
> |
* * If there are too many running threads, suspends this worker |
881 |
> |
* (first forcing inactivation if necessary). If it is not |
882 |
> |
* resumed before a keepAlive elapses, the worker may be "trimmed" |
883 |
> |
* -- killed while suspended within suspendAsSpare. Otherwise, |
884 |
> |
* upon resume it rechecks to make sure that it is still needed. |
885 |
> |
* |
886 |
> |
* @param w the worker |
887 |
> |
* @param retries the number of scans by caller failing to find work |
888 |
> |
* find any (in which case it may block waiting for work). |
889 |
|
*/ |
890 |
< |
final void ensureWorkerInitialization() { |
891 |
< |
ForkJoinWorkerThread[] ws = workers; |
892 |
< |
if (ws == null) { |
893 |
< |
final ReentrantLock lock = this.workerLock; |
894 |
< |
lock.lock(); |
895 |
< |
try { |
896 |
< |
ws = workers; |
897 |
< |
if (ws == null) { |
898 |
< |
int ps = parallelism; |
899 |
< |
ws = ensureWorkerArrayCapacity(ps); |
900 |
< |
for (int i = 0; i < ps; ++i) { |
901 |
< |
ForkJoinWorkerThread w = createWorker(i); |
890 |
> |
final void preStep(ForkJoinWorkerThread w, int retries) { |
891 |
> |
boolean active = w.active; |
892 |
> |
boolean inactivate = active && retries != 0; |
893 |
> |
for (;;) { |
894 |
> |
int rs, wc; |
895 |
> |
if (inactivate && |
896 |
> |
UNSAFE.compareAndSwapInt(this, runStateOffset, |
897 |
> |
rs = runState, rs - ONE_ACTIVE)) |
898 |
> |
inactivate = active = w.active = false; |
899 |
> |
if (((wc = workerCounts) & RUNNING_COUNT_MASK) <= parallelism) { |
900 |
> |
if (active || eventSync(w, retries)) |
901 |
> |
break; |
902 |
> |
} |
903 |
> |
else if (!(inactivate |= active) && // must inactivate to suspend |
904 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
905 |
> |
wc, wc - ONE_RUNNING) && |
906 |
> |
!w.suspendAsSpare()) // false if trimmed |
907 |
> |
break; |
908 |
> |
} |
909 |
> |
} |
910 |
> |
|
911 |
> |
/** |
912 |
> |
* Awaits join of the given task if enough threads, or can resume |
913 |
> |
* or create a spare. Fails (in which case the given task might |
914 |
> |
* not be done) upon contention or lack of decision about |
915 |
> |
* blocking. Returns void because caller must check |
916 |
> |
* task status on return anyway. |
917 |
> |
* |
918 |
> |
* We allow blocking if: |
919 |
> |
* |
920 |
> |
* 1. There would still be at least as many running threads as |
921 |
> |
* parallelism level if this thread blocks. |
922 |
> |
* |
923 |
> |
* 2. A spare is resumed to replace this worker. We tolerate |
924 |
> |
* slop in the decision to replace if a spare is found without |
925 |
> |
* first decrementing run count. This may release too many, |
926 |
> |
* but if so, the superfluous ones will re-suspend via |
927 |
> |
* preStep(). |
928 |
> |
* |
929 |
> |
* 3. After #spares repeated checks, there are no fewer than #spare |
930 |
> |
* threads not running. We allow this slack to avoid hysteresis |
931 |
> |
* and as a hedge against lag/uncertainty of running count |
932 |
> |
* estimates when signalling or unblocking stalls. |
933 |
> |
* |
934 |
> |
* 4. All existing workers are busy (as rechecked via repeated |
935 |
> |
* retries by caller) and a new spare is created. |
936 |
> |
* |
937 |
> |
* If none of the above hold, we try to escape out by |
938 |
> |
* re-incrementing count and returning to caller, which can retry |
939 |
> |
* later. |
940 |
> |
* |
941 |
> |
* @param joinMe the task to join |
942 |
> |
* @param retries if negative, then serve only as a precheck |
943 |
> |
* that the thread can be replaced by a spare. Otherwise, |
944 |
> |
* the number of repeated calls to this method returning busy |
945 |
> |
* @return true if the call must be retried because there |
946 |
> |
* none of the blocking checks hold |
947 |
> |
*/ |
948 |
> |
final boolean tryAwaitJoin(ForkJoinTask<?> joinMe, int retries) { |
949 |
> |
if (joinMe.status < 0) // precheck for cancellation |
950 |
> |
return false; |
951 |
> |
if ((runState & TERMINATING) != 0) { // shutting down |
952 |
> |
joinMe.cancelIgnoringExceptions(); |
953 |
> |
return false; |
954 |
> |
} |
955 |
> |
|
956 |
> |
int pc = parallelism; |
957 |
> |
boolean running = true; // false when running count decremented |
958 |
> |
outer:for (;;) { |
959 |
> |
int wc = workerCounts; |
960 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
961 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
962 |
> |
if (running) { // replace with spare or decrement count |
963 |
> |
if (rc <= pc && tc > pc && |
964 |
> |
(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) { |
965 |
> |
ForkJoinWorkerThread[] ws = workers; |
966 |
> |
int nws = ws.length; |
967 |
> |
for (int i = 0; i < nws; ++i) { // search for spare |
968 |
> |
ForkJoinWorkerThread w = ws[i]; |
969 |
|
if (w != null) { |
970 |
< |
ws[i] = w; |
971 |
< |
w.start(); |
972 |
< |
updateWorkerCount(1); |
970 |
> |
if (joinMe.status < 0) |
971 |
> |
return false; |
972 |
> |
if (w.isSuspended()) { |
973 |
> |
if ((workerCounts & RUNNING_COUNT_MASK)>=pc && |
974 |
> |
w.tryResumeSpare()) { |
975 |
> |
running = false; |
976 |
> |
break outer; |
977 |
> |
} |
978 |
> |
continue outer; // rescan |
979 |
> |
} |
980 |
|
} |
981 |
|
} |
982 |
|
} |
983 |
< |
} finally { |
984 |
< |
lock.unlock(); |
983 |
> |
if (retries < 0 || // < 0 means replacement check only |
984 |
> |
rc == 0 || joinMe.status < 0 || workerCounts != wc || |
985 |
> |
!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
986 |
> |
wc, wc - ONE_RUNNING)) |
987 |
> |
return false; // done or inconsistent or contended |
988 |
> |
running = false; |
989 |
> |
if (rc > pc) |
990 |
> |
break; |
991 |
> |
} |
992 |
> |
else { // allow blocking if enough threads |
993 |
> |
if (rc >= pc || joinMe.status < 0) |
994 |
> |
break; |
995 |
> |
int sc = tc - pc + 1; // = spare threads, plus the one to add |
996 |
> |
if (retries > sc) { |
997 |
> |
if (rc > 0 && rc >= pc - sc) // allow slack |
998 |
> |
break; |
999 |
> |
if (tc < MAX_THREADS && |
1000 |
> |
tc == (runState & ACTIVE_COUNT_MASK) && |
1001 |
> |
workerCounts == wc && |
1002 |
> |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
1003 |
> |
wc+(ONE_RUNNING|ONE_TOTAL))) { |
1004 |
> |
addWorker(); |
1005 |
> |
break; |
1006 |
> |
} |
1007 |
> |
} |
1008 |
> |
if (workerCounts == wc && // back out to allow rescan |
1009 |
> |
UNSAFE.compareAndSwapInt (this, workerCountsOffset, |
1010 |
> |
wc, wc + ONE_RUNNING)) { |
1011 |
> |
releaseWaiters(); // help others progress |
1012 |
> |
return true; // let caller retry |
1013 |
> |
} |
1014 |
|
} |
1015 |
|
} |
1016 |
+ |
// arrive here if can block |
1017 |
+ |
joinMe.internalAwaitDone(); |
1018 |
+ |
int c; // to inline incrementRunningCount |
1019 |
+ |
do {} while (!UNSAFE.compareAndSwapInt |
1020 |
+ |
(this, workerCountsOffset, |
1021 |
+ |
c = workerCounts, c + ONE_RUNNING)); |
1022 |
+ |
return false; |
1023 |
|
} |
1024 |
|
|
1025 |
|
/** |
1026 |
< |
* Worker creation and startup for threads added via setParallelism. |
1026 |
> |
* Same idea as (and shares many code snippets with) tryAwaitJoin, |
1027 |
> |
* but self-contained because there are no caller retries. |
1028 |
> |
* TODO: Rework to use simpler API. |
1029 |
|
*/ |
1030 |
< |
private void createAndStartAddedWorkers() { |
1031 |
< |
resumeAllSpares(); // Allow spares to convert to nonspare |
1032 |
< |
int ps = parallelism; |
1033 |
< |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
1034 |
< |
int len = ws.length; |
1035 |
< |
// Sweep through slots, to keep lowest indices most populated |
1036 |
< |
int k = 0; |
1037 |
< |
while (k < len) { |
1038 |
< |
if (ws[k] != null) { |
1039 |
< |
++k; |
1040 |
< |
continue; |
1041 |
< |
} |
1042 |
< |
int s = workerCounts; |
1043 |
< |
int tc = totalCountOf(s); |
1044 |
< |
int rc = runningCountOf(s); |
1045 |
< |
if (rc >= ps || tc >= ps) |
1046 |
< |
break; |
1047 |
< |
if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) { |
1048 |
< |
ForkJoinWorkerThread w = createWorker(k); |
1049 |
< |
if (w != null) { |
1050 |
< |
ws[k++] = w; |
1051 |
< |
w.start(); |
1030 |
> |
final void awaitBlocker(ManagedBlocker blocker) |
1031 |
> |
throws InterruptedException { |
1032 |
> |
boolean done; |
1033 |
> |
if (done = blocker.isReleasable()) |
1034 |
> |
return; |
1035 |
> |
int pc = parallelism; |
1036 |
> |
int retries = 0; |
1037 |
> |
boolean running = true; // false when running count decremented |
1038 |
> |
outer:for (;;) { |
1039 |
> |
int wc = workerCounts; |
1040 |
> |
int rc = wc & RUNNING_COUNT_MASK; |
1041 |
> |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
1042 |
> |
if (running) { |
1043 |
> |
if (rc <= pc && tc > pc && |
1044 |
> |
(retries > 0 || tc > (runState & ACTIVE_COUNT_MASK))) { |
1045 |
> |
ForkJoinWorkerThread[] ws = workers; |
1046 |
> |
int nws = ws.length; |
1047 |
> |
for (int i = 0; i < nws; ++i) { |
1048 |
> |
ForkJoinWorkerThread w = ws[i]; |
1049 |
> |
if (w != null) { |
1050 |
> |
if (done = blocker.isReleasable()) |
1051 |
> |
return; |
1052 |
> |
if (w.isSuspended()) { |
1053 |
> |
if ((workerCounts & RUNNING_COUNT_MASK)>=pc && |
1054 |
> |
w.tryResumeSpare()) { |
1055 |
> |
running = false; |
1056 |
> |
break outer; |
1057 |
> |
} |
1058 |
> |
continue outer; // rescan |
1059 |
> |
} |
1060 |
> |
} |
1061 |
> |
} |
1062 |
|
} |
1063 |
< |
else { |
1064 |
< |
updateWorkerCount(-1); // back out on failed creation |
1063 |
> |
if (done = blocker.isReleasable()) |
1064 |
> |
return; |
1065 |
> |
if (rc == 0 || workerCounts != wc || |
1066 |
> |
!UNSAFE.compareAndSwapInt(this, workerCountsOffset, |
1067 |
> |
wc, wc - ONE_RUNNING)) |
1068 |
> |
continue; |
1069 |
> |
running = false; |
1070 |
> |
if (rc > pc) |
1071 |
|
break; |
1072 |
+ |
} |
1073 |
+ |
else { |
1074 |
+ |
if (rc >= pc || (done = blocker.isReleasable())) |
1075 |
+ |
break; |
1076 |
+ |
int sc = tc - pc + 1; |
1077 |
+ |
if (retries++ > sc) { |
1078 |
+ |
if (rc > 0 && rc >= pc - sc) |
1079 |
+ |
break; |
1080 |
+ |
if (tc < MAX_THREADS && |
1081 |
+ |
tc == (runState & ACTIVE_COUNT_MASK) && |
1082 |
+ |
workerCounts == wc && |
1083 |
+ |
UNSAFE.compareAndSwapInt(this, workerCountsOffset, wc, |
1084 |
+ |
wc+(ONE_RUNNING|ONE_TOTAL))) { |
1085 |
+ |
addWorker(); |
1086 |
+ |
break; |
1087 |
+ |
} |
1088 |
+ |
} |
1089 |
+ |
Thread.yield(); |
1090 |
+ |
} |
1091 |
+ |
} |
1092 |
+ |
|
1093 |
+ |
try { |
1094 |
+ |
if (!done) |
1095 |
+ |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1096 |
+ |
} finally { |
1097 |
+ |
if (!running) { |
1098 |
+ |
int c; |
1099 |
+ |
do {} while (!UNSAFE.compareAndSwapInt |
1100 |
+ |
(this, workerCountsOffset, |
1101 |
+ |
c = workerCounts, c + ONE_RUNNING)); |
1102 |
+ |
} |
1103 |
+ |
} |
1104 |
+ |
} |
1105 |
+ |
|
1106 |
+ |
/** |
1107 |
+ |
* Possibly initiates and/or completes termination. |
1108 |
+ |
* |
1109 |
+ |
* @param now if true, unconditionally terminate, else only |
1110 |
+ |
* if shutdown and empty queue and no active workers |
1111 |
+ |
* @return true if now terminating or terminated |
1112 |
+ |
*/ |
1113 |
+ |
private boolean tryTerminate(boolean now) { |
1114 |
+ |
if (now) |
1115 |
+ |
advanceRunLevel(SHUTDOWN); // ensure at least SHUTDOWN |
1116 |
+ |
else if (runState < SHUTDOWN || |
1117 |
+ |
!submissionQueue.isEmpty() || |
1118 |
+ |
(runState & ACTIVE_COUNT_MASK) != 0) |
1119 |
+ |
return false; |
1120 |
+ |
|
1121 |
+ |
if (advanceRunLevel(TERMINATING)) |
1122 |
+ |
startTerminating(); |
1123 |
+ |
|
1124 |
+ |
// Finish now if all threads terminated; else in some subsequent call |
1125 |
+ |
if ((workerCounts >>> TOTAL_COUNT_SHIFT) == 0) { |
1126 |
+ |
advanceRunLevel(TERMINATED); |
1127 |
+ |
termination.arrive(); |
1128 |
+ |
} |
1129 |
+ |
return true; |
1130 |
+ |
} |
1131 |
+ |
|
1132 |
+ |
/** |
1133 |
+ |
* Actions on transition to TERMINATING |
1134 |
+ |
*/ |
1135 |
+ |
private void startTerminating() { |
1136 |
+ |
for (int i = 0; i < 2; ++i) { // twice to mop up newly created workers |
1137 |
+ |
cancelSubmissions(); |
1138 |
+ |
shutdownWorkers(); |
1139 |
+ |
cancelWorkerTasks(); |
1140 |
+ |
signalEvent(); |
1141 |
+ |
interruptWorkers(); |
1142 |
+ |
} |
1143 |
+ |
} |
1144 |
+ |
|
1145 |
+ |
/** |
1146 |
+ |
* Clear out and cancel submissions, ignoring exceptions |
1147 |
+ |
*/ |
1148 |
+ |
private void cancelSubmissions() { |
1149 |
+ |
ForkJoinTask<?> task; |
1150 |
+ |
while ((task = submissionQueue.poll()) != null) { |
1151 |
+ |
try { |
1152 |
+ |
task.cancel(false); |
1153 |
+ |
} catch (Throwable ignore) { |
1154 |
+ |
} |
1155 |
+ |
} |
1156 |
+ |
} |
1157 |
+ |
|
1158 |
+ |
/** |
1159 |
+ |
* Sets all worker run states to at least shutdown, |
1160 |
+ |
* also resuming suspended workers |
1161 |
+ |
*/ |
1162 |
+ |
private void shutdownWorkers() { |
1163 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1164 |
+ |
int nws = ws.length; |
1165 |
+ |
for (int i = 0; i < nws; ++i) { |
1166 |
+ |
ForkJoinWorkerThread w = ws[i]; |
1167 |
+ |
if (w != null) |
1168 |
+ |
w.shutdown(); |
1169 |
+ |
} |
1170 |
+ |
} |
1171 |
+ |
|
1172 |
+ |
/** |
1173 |
+ |
* Clears out and cancels all locally queued tasks |
1174 |
+ |
*/ |
1175 |
+ |
private void cancelWorkerTasks() { |
1176 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1177 |
+ |
int nws = ws.length; |
1178 |
+ |
for (int i = 0; i < nws; ++i) { |
1179 |
+ |
ForkJoinWorkerThread w = ws[i]; |
1180 |
+ |
if (w != null) |
1181 |
+ |
w.cancelTasks(); |
1182 |
+ |
} |
1183 |
+ |
} |
1184 |
+ |
|
1185 |
+ |
/** |
1186 |
+ |
* Unsticks all workers blocked on joins etc |
1187 |
+ |
*/ |
1188 |
+ |
private void interruptWorkers() { |
1189 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1190 |
+ |
int nws = ws.length; |
1191 |
+ |
for (int i = 0; i < nws; ++i) { |
1192 |
+ |
ForkJoinWorkerThread w = ws[i]; |
1193 |
+ |
if (w != null && !w.isTerminated()) { |
1194 |
+ |
try { |
1195 |
+ |
w.interrupt(); |
1196 |
+ |
} catch (SecurityException ignore) { |
1197 |
|
} |
1198 |
|
} |
1199 |
|
} |
1200 |
|
} |
1201 |
|
|
1202 |
+ |
// misc support for ForkJoinWorkerThread |
1203 |
+ |
|
1204 |
+ |
/** |
1205 |
+ |
* Returns pool number |
1206 |
+ |
*/ |
1207 |
+ |
final int getPoolNumber() { |
1208 |
+ |
return poolNumber; |
1209 |
+ |
} |
1210 |
+ |
|
1211 |
+ |
/** |
1212 |
+ |
* Accumulates steal count from a worker, clearing |
1213 |
+ |
* the worker's value |
1214 |
+ |
*/ |
1215 |
+ |
final void accumulateStealCount(ForkJoinWorkerThread w) { |
1216 |
+ |
int sc = w.stealCount; |
1217 |
+ |
if (sc != 0) { |
1218 |
+ |
long c; |
1219 |
+ |
w.stealCount = 0; |
1220 |
+ |
do {} while (!UNSAFE.compareAndSwapLong(this, stealCountOffset, |
1221 |
+ |
c = stealCount, c + sc)); |
1222 |
+ |
} |
1223 |
+ |
} |
1224 |
+ |
|
1225 |
+ |
/** |
1226 |
+ |
* Returns the approximate (non-atomic) number of idle threads per |
1227 |
+ |
* active thread. |
1228 |
+ |
*/ |
1229 |
+ |
final int idlePerActive() { |
1230 |
+ |
int pc = parallelism; // use parallelism, not rc |
1231 |
+ |
int ac = runState; // no mask -- artifically boosts during shutdown |
1232 |
+ |
// Use exact results for small values, saturate past 4 |
1233 |
+ |
return pc <= ac? 0 : pc >>> 1 <= ac? 1 : pc >>> 2 <= ac? 3 : pc >>> 3; |
1234 |
+ |
} |
1235 |
+ |
|
1236 |
+ |
// Public and protected methods |
1237 |
+ |
|
1238 |
+ |
// Constructors |
1239 |
+ |
|
1240 |
+ |
/** |
1241 |
+ |
* Creates a {@code ForkJoinPool} with parallelism equal to {@link |
1242 |
+ |
* java.lang.Runtime#availableProcessors}, using the {@linkplain |
1243 |
+ |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1244 |
+ |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1245 |
+ |
* |
1246 |
+ |
* @throws SecurityException if a security manager exists and |
1247 |
+ |
* the caller is not permitted to modify threads |
1248 |
+ |
* because it does not hold {@link |
1249 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1250 |
+ |
*/ |
1251 |
+ |
public ForkJoinPool() { |
1252 |
+ |
this(Runtime.getRuntime().availableProcessors(), |
1253 |
+ |
defaultForkJoinWorkerThreadFactory, null, false); |
1254 |
+ |
} |
1255 |
+ |
|
1256 |
+ |
/** |
1257 |
+ |
* Creates a {@code ForkJoinPool} with the indicated parallelism |
1258 |
+ |
* level, the {@linkplain |
1259 |
+ |
* #defaultForkJoinWorkerThreadFactory default thread factory}, |
1260 |
+ |
* no UncaughtExceptionHandler, and non-async LIFO processing mode. |
1261 |
+ |
* |
1262 |
+ |
* @param parallelism the parallelism level |
1263 |
+ |
* @throws IllegalArgumentException if parallelism less than or |
1264 |
+ |
* equal to zero, or greater than implementation limit |
1265 |
+ |
* @throws SecurityException if a security manager exists and |
1266 |
+ |
* the caller is not permitted to modify threads |
1267 |
+ |
* because it does not hold {@link |
1268 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1269 |
+ |
*/ |
1270 |
+ |
public ForkJoinPool(int parallelism) { |
1271 |
+ |
this(parallelism, defaultForkJoinWorkerThreadFactory, null, false); |
1272 |
+ |
} |
1273 |
+ |
|
1274 |
+ |
/** |
1275 |
+ |
* Creates a {@code ForkJoinPool} with the given parameters. |
1276 |
+ |
* |
1277 |
+ |
* @param parallelism the parallelism level. For default value, |
1278 |
+ |
* use {@link java.lang.Runtime#availableProcessors}. |
1279 |
+ |
* @param factory the factory for creating new threads. For default value, |
1280 |
+ |
* use {@link #defaultForkJoinWorkerThreadFactory}. |
1281 |
+ |
* @param handler the handler for internal worker threads that |
1282 |
+ |
* terminate due to unrecoverable errors encountered while executing |
1283 |
+ |
* tasks. For default value, use <code>null</code>. |
1284 |
+ |
* @param asyncMode if true, |
1285 |
+ |
* establishes local first-in-first-out scheduling mode for forked |
1286 |
+ |
* tasks that are never joined. This mode may be more appropriate |
1287 |
+ |
* than default locally stack-based mode in applications in which |
1288 |
+ |
* worker threads only process event-style asynchronous tasks. |
1289 |
+ |
* For default value, use <code>false</code>. |
1290 |
+ |
* @throws IllegalArgumentException if parallelism less than or |
1291 |
+ |
* equal to zero, or greater than implementation limit |
1292 |
+ |
* @throws NullPointerException if the factory is null |
1293 |
+ |
* @throws SecurityException if a security manager exists and |
1294 |
+ |
* the caller is not permitted to modify threads |
1295 |
+ |
* because it does not hold {@link |
1296 |
+ |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1297 |
+ |
*/ |
1298 |
+ |
public ForkJoinPool(int parallelism, |
1299 |
+ |
ForkJoinWorkerThreadFactory factory, |
1300 |
+ |
Thread.UncaughtExceptionHandler handler, |
1301 |
+ |
boolean asyncMode) { |
1302 |
+ |
checkPermission(); |
1303 |
+ |
if (factory == null) |
1304 |
+ |
throw new NullPointerException(); |
1305 |
+ |
if (parallelism <= 0 || parallelism > MAX_THREADS) |
1306 |
+ |
throw new IllegalArgumentException(); |
1307 |
+ |
this.parallelism = parallelism; |
1308 |
+ |
this.factory = factory; |
1309 |
+ |
this.ueh = handler; |
1310 |
+ |
this.locallyFifo = asyncMode; |
1311 |
+ |
int arraySize = initialArraySizeFor(parallelism); |
1312 |
+ |
this.workers = new ForkJoinWorkerThread[arraySize]; |
1313 |
+ |
this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
1314 |
+ |
this.workerLock = new ReentrantLock(); |
1315 |
+ |
this.termination = new Phaser(1); |
1316 |
+ |
this.poolNumber = poolNumberGenerator.incrementAndGet(); |
1317 |
+ |
} |
1318 |
+ |
|
1319 |
+ |
/** |
1320 |
+ |
* Returns initial power of two size for workers array. |
1321 |
+ |
* @param pc the initial parallelism level |
1322 |
+ |
*/ |
1323 |
+ |
private static int initialArraySizeFor(int pc) { |
1324 |
+ |
// See Hackers Delight, sec 3.2. We know MAX_THREADS < (1 >>> 16) |
1325 |
+ |
int size = pc < MAX_THREADS ? pc + 1 : MAX_THREADS; |
1326 |
+ |
size |= size >>> 1; |
1327 |
+ |
size |= size >>> 2; |
1328 |
+ |
size |= size >>> 4; |
1329 |
+ |
size |= size >>> 8; |
1330 |
+ |
return size + 1; |
1331 |
+ |
} |
1332 |
+ |
|
1333 |
|
// Execution methods |
1334 |
|
|
1335 |
|
/** |
1336 |
|
* Common code for execute, invoke and submit |
1337 |
|
*/ |
1338 |
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
1339 |
< |
if (isShutdown()) |
1339 |
> |
if (task == null) |
1340 |
> |
throw new NullPointerException(); |
1341 |
> |
if (runState >= SHUTDOWN) |
1342 |
|
throw new RejectedExecutionException(); |
532 |
– |
if (workers == null) |
533 |
– |
ensureWorkerInitialization(); |
1343 |
|
submissionQueue.offer(task); |
1344 |
< |
signalIdleWorkers(); |
1344 |
> |
signalEvent(); |
1345 |
> |
ensureEnoughWorkers(); |
1346 |
|
} |
1347 |
|
|
1348 |
|
/** |
1349 |
< |
* Performs the given task; returning its result upon completion |
1349 |
> |
* Performs the given task, returning its result upon completion. |
1350 |
> |
* If the caller is already engaged in a fork/join computation in |
1351 |
> |
* the current pool, this method is equivalent in effect to |
1352 |
> |
* {@link ForkJoinTask#invoke}. |
1353 |
> |
* |
1354 |
|
* @param task the task |
1355 |
|
* @return the task's result |
1356 |
< |
* @throws NullPointerException if task is null |
1357 |
< |
* @throws RejectedExecutionException if pool is shut down |
1356 |
> |
* @throws NullPointerException if the task is null |
1357 |
> |
* @throws RejectedExecutionException if the task cannot be |
1358 |
> |
* scheduled for execution |
1359 |
|
*/ |
1360 |
|
public <T> T invoke(ForkJoinTask<T> task) { |
1361 |
|
doSubmit(task); |
1364 |
|
|
1365 |
|
/** |
1366 |
|
* Arranges for (asynchronous) execution of the given task. |
1367 |
+ |
* If the caller is already engaged in a fork/join computation in |
1368 |
+ |
* the current pool, this method is equivalent in effect to |
1369 |
+ |
* {@link ForkJoinTask#fork}. |
1370 |
+ |
* |
1371 |
|
* @param task the task |
1372 |
< |
* @throws NullPointerException if task is null |
1373 |
< |
* @throws RejectedExecutionException if pool is shut down |
1372 |
> |
* @throws NullPointerException if the task is null |
1373 |
> |
* @throws RejectedExecutionException if the task cannot be |
1374 |
> |
* scheduled for execution |
1375 |
|
*/ |
1376 |
< |
public <T> void execute(ForkJoinTask<T> task) { |
1376 |
> |
public void execute(ForkJoinTask<?> task) { |
1377 |
|
doSubmit(task); |
1378 |
|
} |
1379 |
|
|
1380 |
|
// AbstractExecutorService methods |
1381 |
|
|
1382 |
+ |
/** |
1383 |
+ |
* @throws NullPointerException if the task is null |
1384 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1385 |
+ |
* scheduled for execution |
1386 |
+ |
*/ |
1387 |
|
public void execute(Runnable task) { |
1388 |
< |
doSubmit(new AdaptedRunnable<Void>(task, null)); |
1388 |
> |
ForkJoinTask<?> job; |
1389 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1390 |
> |
job = (ForkJoinTask<?>) task; |
1391 |
> |
else |
1392 |
> |
job = ForkJoinTask.adapt(task, null); |
1393 |
> |
doSubmit(job); |
1394 |
> |
} |
1395 |
> |
|
1396 |
> |
/** |
1397 |
> |
* Submits a ForkJoinTask for execution. |
1398 |
> |
* If the caller is already engaged in a fork/join computation in |
1399 |
> |
* the current pool, this method is equivalent in effect to |
1400 |
> |
* {@link ForkJoinTask#fork}. |
1401 |
> |
* |
1402 |
> |
* @param task the task to submit |
1403 |
> |
* @return the task |
1404 |
> |
* @throws NullPointerException if the task is null |
1405 |
> |
* @throws RejectedExecutionException if the task cannot be |
1406 |
> |
* scheduled for execution |
1407 |
> |
*/ |
1408 |
> |
public <T> ForkJoinTask<T> submit(ForkJoinTask<T> task) { |
1409 |
> |
doSubmit(task); |
1410 |
> |
return task; |
1411 |
|
} |
1412 |
|
|
1413 |
+ |
/** |
1414 |
+ |
* @throws NullPointerException if the task is null |
1415 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1416 |
+ |
* scheduled for execution |
1417 |
+ |
*/ |
1418 |
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
1419 |
< |
ForkJoinTask<T> job = new AdaptedCallable<T>(task); |
1419 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task); |
1420 |
|
doSubmit(job); |
1421 |
|
return job; |
1422 |
|
} |
1423 |
|
|
1424 |
+ |
/** |
1425 |
+ |
* @throws NullPointerException if the task is null |
1426 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1427 |
+ |
* scheduled for execution |
1428 |
+ |
*/ |
1429 |
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
1430 |
< |
ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result); |
1430 |
> |
ForkJoinTask<T> job = ForkJoinTask.adapt(task, result); |
1431 |
|
doSubmit(job); |
1432 |
|
return job; |
1433 |
|
} |
1434 |
|
|
1435 |
+ |
/** |
1436 |
+ |
* @throws NullPointerException if the task is null |
1437 |
+ |
* @throws RejectedExecutionException if the task cannot be |
1438 |
+ |
* scheduled for execution |
1439 |
+ |
*/ |
1440 |
|
public ForkJoinTask<?> submit(Runnable task) { |
1441 |
< |
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
1441 |
> |
ForkJoinTask<?> job; |
1442 |
> |
if (task instanceof ForkJoinTask<?>) // avoid re-wrap |
1443 |
> |
job = (ForkJoinTask<?>) task; |
1444 |
> |
else |
1445 |
> |
job = ForkJoinTask.adapt(task, null); |
1446 |
|
doSubmit(job); |
1447 |
|
return job; |
1448 |
|
} |
1449 |
|
|
1450 |
|
/** |
1451 |
< |
* Adaptor for Runnables. This implements RunnableFuture |
1452 |
< |
* to be compliant with AbstractExecutorService constraints |
1451 |
> |
* @throws NullPointerException {@inheritDoc} |
1452 |
> |
* @throws RejectedExecutionException {@inheritDoc} |
1453 |
|
*/ |
588 |
– |
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
589 |
– |
implements RunnableFuture<T> { |
590 |
– |
final Runnable runnable; |
591 |
– |
final T resultOnCompletion; |
592 |
– |
T result; |
593 |
– |
AdaptedRunnable(Runnable runnable, T result) { |
594 |
– |
if (runnable == null) throw new NullPointerException(); |
595 |
– |
this.runnable = runnable; |
596 |
– |
this.resultOnCompletion = result; |
597 |
– |
} |
598 |
– |
public T getRawResult() { return result; } |
599 |
– |
public void setRawResult(T v) { result = v; } |
600 |
– |
public boolean exec() { |
601 |
– |
runnable.run(); |
602 |
– |
result = resultOnCompletion; |
603 |
– |
return true; |
604 |
– |
} |
605 |
– |
public void run() { invoke(); } |
606 |
– |
} |
607 |
– |
|
608 |
– |
/** |
609 |
– |
* Adaptor for Callables |
610 |
– |
*/ |
611 |
– |
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
612 |
– |
implements RunnableFuture<T> { |
613 |
– |
final Callable<T> callable; |
614 |
– |
T result; |
615 |
– |
AdaptedCallable(Callable<T> callable) { |
616 |
– |
if (callable == null) throw new NullPointerException(); |
617 |
– |
this.callable = callable; |
618 |
– |
} |
619 |
– |
public T getRawResult() { return result; } |
620 |
– |
public void setRawResult(T v) { result = v; } |
621 |
– |
public boolean exec() { |
622 |
– |
try { |
623 |
– |
result = callable.call(); |
624 |
– |
return true; |
625 |
– |
} catch (Error err) { |
626 |
– |
throw err; |
627 |
– |
} catch (RuntimeException rex) { |
628 |
– |
throw rex; |
629 |
– |
} catch (Exception ex) { |
630 |
– |
throw new RuntimeException(ex); |
631 |
– |
} |
632 |
– |
} |
633 |
– |
public void run() { invoke(); } |
634 |
– |
} |
635 |
– |
|
1454 |
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
1455 |
< |
ArrayList<ForkJoinTask<T>> ts = |
1455 |
> |
ArrayList<ForkJoinTask<T>> forkJoinTasks = |
1456 |
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
1457 |
< |
for (Callable<T> c : tasks) |
1458 |
< |
ts.add(new AdaptedCallable<T>(c)); |
1459 |
< |
invoke(new InvokeAll<T>(ts)); |
1460 |
< |
return (List<Future<T>>)(List)ts; |
1457 |
> |
for (Callable<T> task : tasks) |
1458 |
> |
forkJoinTasks.add(ForkJoinTask.adapt(task)); |
1459 |
> |
invoke(new InvokeAll<T>(forkJoinTasks)); |
1460 |
> |
|
1461 |
> |
@SuppressWarnings({"unchecked", "rawtypes"}) |
1462 |
> |
List<Future<T>> futures = (List<Future<T>>) (List) forkJoinTasks; |
1463 |
> |
return futures; |
1464 |
|
} |
1465 |
|
|
1466 |
|
static final class InvokeAll<T> extends RecursiveAction { |
1467 |
|
final ArrayList<ForkJoinTask<T>> tasks; |
1468 |
|
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
1469 |
|
public void compute() { |
1470 |
< |
try { invokeAll(tasks); } catch(Exception ignore) {} |
1470 |
> |
try { invokeAll(tasks); } |
1471 |
> |
catch (Exception ignore) {} |
1472 |
|
} |
1473 |
+ |
private static final long serialVersionUID = -7914297376763021607L; |
1474 |
|
} |
1475 |
|
|
653 |
– |
// Configuration and status settings and queries |
654 |
– |
|
1476 |
|
/** |
1477 |
< |
* Returns the factory used for constructing new workers |
1477 |
> |
* Returns the factory used for constructing new workers. |
1478 |
|
* |
1479 |
|
* @return the factory used for constructing new workers |
1480 |
|
*/ |
1485 |
|
/** |
1486 |
|
* Returns the handler for internal worker threads that terminate |
1487 |
|
* due to unrecoverable errors encountered while executing tasks. |
667 |
– |
* @return the handler, or null if none |
668 |
– |
*/ |
669 |
– |
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
670 |
– |
Thread.UncaughtExceptionHandler h; |
671 |
– |
final ReentrantLock lock = this.workerLock; |
672 |
– |
lock.lock(); |
673 |
– |
try { |
674 |
– |
h = ueh; |
675 |
– |
} finally { |
676 |
– |
lock.unlock(); |
677 |
– |
} |
678 |
– |
return h; |
679 |
– |
} |
680 |
– |
|
681 |
– |
/** |
682 |
– |
* Sets the handler for internal worker threads that terminate due |
683 |
– |
* to unrecoverable errors encountered while executing tasks. |
684 |
– |
* Unless set, the current default or ThreadGroup handler is used |
685 |
– |
* as handler. |
1488 |
|
* |
1489 |
< |
* @param h the new handler |
688 |
< |
* @return the old handler, or null if none |
689 |
< |
* @throws SecurityException if a security manager exists and |
690 |
< |
* the caller is not permitted to modify threads |
691 |
< |
* because it does not hold {@link |
692 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1489 |
> |
* @return the handler, or {@code null} if none |
1490 |
|
*/ |
1491 |
< |
public Thread.UncaughtExceptionHandler |
1492 |
< |
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
696 |
< |
checkPermission(); |
697 |
< |
Thread.UncaughtExceptionHandler old = null; |
698 |
< |
final ReentrantLock lock = this.workerLock; |
699 |
< |
lock.lock(); |
700 |
< |
try { |
701 |
< |
old = ueh; |
702 |
< |
ueh = h; |
703 |
< |
ForkJoinWorkerThread[] ws = workers; |
704 |
< |
if (ws != null) { |
705 |
< |
for (int i = 0; i < ws.length; ++i) { |
706 |
< |
ForkJoinWorkerThread w = ws[i]; |
707 |
< |
if (w != null) |
708 |
< |
w.setUncaughtExceptionHandler(h); |
709 |
< |
} |
710 |
< |
} |
711 |
< |
} finally { |
712 |
< |
lock.unlock(); |
713 |
< |
} |
714 |
< |
return old; |
715 |
< |
} |
716 |
< |
|
717 |
< |
|
718 |
< |
/** |
719 |
< |
* Sets the target paralleism level of this pool. |
720 |
< |
* @param parallelism the target parallelism |
721 |
< |
* @throws IllegalArgumentException if parallelism less than or |
722 |
< |
* equal to zero or greater than maximum size bounds. |
723 |
< |
* @throws SecurityException if a security manager exists and |
724 |
< |
* the caller is not permitted to modify threads |
725 |
< |
* because it does not hold {@link |
726 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
727 |
< |
*/ |
728 |
< |
public void setParallelism(int parallelism) { |
729 |
< |
checkPermission(); |
730 |
< |
if (parallelism <= 0 || parallelism > maxPoolSize) |
731 |
< |
throw new IllegalArgumentException(); |
732 |
< |
final ReentrantLock lock = this.workerLock; |
733 |
< |
lock.lock(); |
734 |
< |
try { |
735 |
< |
if (!isTerminating()) { |
736 |
< |
int p = this.parallelism; |
737 |
< |
this.parallelism = parallelism; |
738 |
< |
if (parallelism > p) |
739 |
< |
createAndStartAddedWorkers(); |
740 |
< |
else |
741 |
< |
trimSpares(); |
742 |
< |
} |
743 |
< |
} finally { |
744 |
< |
lock.unlock(); |
745 |
< |
} |
746 |
< |
signalIdleWorkers(); |
1491 |
> |
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
1492 |
> |
return ueh; |
1493 |
|
} |
1494 |
|
|
1495 |
|
/** |
1496 |
< |
* Returns the targeted number of worker threads in this pool. |
1496 |
> |
* Returns the targeted parallelism level of this pool. |
1497 |
|
* |
1498 |
< |
* @return the targeted number of worker threads in this pool |
1498 |
> |
* @return the targeted parallelism level of this pool |
1499 |
|
*/ |
1500 |
|
public int getParallelism() { |
1501 |
|
return parallelism; |
1504 |
|
/** |
1505 |
|
* Returns the number of worker threads that have started but not |
1506 |
|
* yet terminated. This result returned by this method may differ |
1507 |
< |
* from <code>getParallelism</code> when threads are created to |
1507 |
> |
* from {@link #getParallelism} when threads are created to |
1508 |
|
* maintain parallelism when others are cooperatively blocked. |
1509 |
|
* |
1510 |
|
* @return the number of worker threads |
1511 |
|
*/ |
1512 |
|
public int getPoolSize() { |
1513 |
< |
return totalCountOf(workerCounts); |
768 |
< |
} |
769 |
< |
|
770 |
< |
/** |
771 |
< |
* Returns the maximum number of threads allowed to exist in the |
772 |
< |
* pool, even if there are insufficient unblocked running threads. |
773 |
< |
* @return the maximum |
774 |
< |
*/ |
775 |
< |
public int getMaximumPoolSize() { |
776 |
< |
return maxPoolSize; |
777 |
< |
} |
778 |
< |
|
779 |
< |
/** |
780 |
< |
* Sets the maximum number of threads allowed to exist in the |
781 |
< |
* pool, even if there are insufficient unblocked running threads. |
782 |
< |
* Setting this value has no effect on current pool size. It |
783 |
< |
* controls construction of new threads. |
784 |
< |
* @throws IllegalArgumentException if negative or greater then |
785 |
< |
* internal implementation limit. |
786 |
< |
*/ |
787 |
< |
public void setMaximumPoolSize(int newMax) { |
788 |
< |
if (newMax < 0 || newMax > MAX_THREADS) |
789 |
< |
throw new IllegalArgumentException(); |
790 |
< |
maxPoolSize = newMax; |
791 |
< |
} |
792 |
< |
|
793 |
< |
|
794 |
< |
/** |
795 |
< |
* Returns true if this pool dynamically maintains its target |
796 |
< |
* parallelism level. If false, new threads are added only to |
797 |
< |
* avoid possible starvation. |
798 |
< |
* This setting is by default true; |
799 |
< |
* @return true if maintains parallelism |
800 |
< |
*/ |
801 |
< |
public boolean getMaintainsParallelism() { |
802 |
< |
return maintainsParallelism; |
803 |
< |
} |
804 |
< |
|
805 |
< |
/** |
806 |
< |
* Sets whether this pool dynamically maintains its target |
807 |
< |
* parallelism level. If false, new threads are added only to |
808 |
< |
* avoid possible starvation. |
809 |
< |
* @param enable true to maintains parallelism |
810 |
< |
*/ |
811 |
< |
public void setMaintainsParallelism(boolean enable) { |
812 |
< |
maintainsParallelism = enable; |
1513 |
> |
return workerCounts >>> TOTAL_COUNT_SHIFT; |
1514 |
|
} |
1515 |
|
|
1516 |
|
/** |
1517 |
< |
* Establishes local first-in-first-out scheduling mode for forked |
1518 |
< |
* tasks that are never joined. This mode may be more appropriate |
818 |
< |
* than default locally stack-based mode in applications in which |
819 |
< |
* worker threads only process asynchronous tasks. This method is |
820 |
< |
* designed to be invoked only when pool is quiescent, and |
821 |
< |
* typically only before any tasks are submitted. The effects of |
822 |
< |
* invocations at ather times may be unpredictable. |
823 |
< |
* |
824 |
< |
* @param async if true, use locally FIFO scheduling |
825 |
< |
* @return the previous mode. |
826 |
< |
*/ |
827 |
< |
public boolean setAsyncMode(boolean async) { |
828 |
< |
boolean oldMode = locallyFifo; |
829 |
< |
locallyFifo = async; |
830 |
< |
ForkJoinWorkerThread[] ws = workers; |
831 |
< |
if (ws != null) { |
832 |
< |
for (int i = 0; i < ws.length; ++i) { |
833 |
< |
ForkJoinWorkerThread t = ws[i]; |
834 |
< |
if (t != null) |
835 |
< |
t.setAsyncMode(async); |
836 |
< |
} |
837 |
< |
} |
838 |
< |
return oldMode; |
839 |
< |
} |
840 |
< |
|
841 |
< |
/** |
842 |
< |
* Returns true if this pool uses local first-in-first-out |
843 |
< |
* scheduling mode for forked tasks that are never joined. |
1517 |
> |
* Returns {@code true} if this pool uses local first-in-first-out |
1518 |
> |
* scheduling mode for forked tasks that are never joined. |
1519 |
|
* |
1520 |
< |
* @return true if this pool uses async mode. |
1520 |
> |
* @return {@code true} if this pool uses async mode |
1521 |
|
*/ |
1522 |
|
public boolean getAsyncMode() { |
1523 |
|
return locallyFifo; |
1526 |
|
/** |
1527 |
|
* Returns an estimate of the number of worker threads that are |
1528 |
|
* not blocked waiting to join tasks or for other managed |
1529 |
< |
* synchronization. |
1529 |
> |
* synchronization. This method may overestimate the |
1530 |
> |
* number of running threads. |
1531 |
|
* |
1532 |
|
* @return the number of worker threads |
1533 |
|
*/ |
1534 |
|
public int getRunningThreadCount() { |
1535 |
< |
return runningCountOf(workerCounts); |
1535 |
> |
return workerCounts & RUNNING_COUNT_MASK; |
1536 |
|
} |
1537 |
|
|
1538 |
|
/** |
1539 |
|
* Returns an estimate of the number of threads that are currently |
1540 |
|
* stealing or executing tasks. This method may overestimate the |
1541 |
|
* number of active threads. |
1542 |
< |
* @return the number of active threads. |
1542 |
> |
* |
1543 |
> |
* @return the number of active threads |
1544 |
|
*/ |
1545 |
|
public int getActiveThreadCount() { |
1546 |
< |
return activeCountOf(runControl); |
1546 |
> |
return runState & ACTIVE_COUNT_MASK; |
1547 |
|
} |
1548 |
|
|
1549 |
|
/** |
1550 |
< |
* Returns an estimate of the number of threads that are currently |
1551 |
< |
* idle waiting for tasks. This method may underestimate the |
1552 |
< |
* number of idle threads. |
1553 |
< |
* @return the number of idle threads. |
1554 |
< |
*/ |
1555 |
< |
final int getIdleThreadCount() { |
1556 |
< |
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
1557 |
< |
return (c <= 0)? 0 : c; |
1558 |
< |
} |
882 |
< |
|
883 |
< |
/** |
884 |
< |
* Returns true if all worker threads are currently idle. An idle |
885 |
< |
* worker is one that cannot obtain a task to execute because none |
886 |
< |
* are available to steal from other threads, and there are no |
887 |
< |
* pending submissions to the pool. This method is conservative: |
888 |
< |
* It might not return true immediately upon idleness of all |
889 |
< |
* threads, but will eventually become true if threads remain |
890 |
< |
* inactive. |
891 |
< |
* @return true if all threads are currently idle |
1550 |
> |
* Returns {@code true} if all worker threads are currently idle. |
1551 |
> |
* An idle worker is one that cannot obtain a task to execute |
1552 |
> |
* because none are available to steal from other threads, and |
1553 |
> |
* there are no pending submissions to the pool. This method is |
1554 |
> |
* conservative; it might not return {@code true} immediately upon |
1555 |
> |
* idleness of all threads, but will eventually become true if |
1556 |
> |
* threads remain inactive. |
1557 |
> |
* |
1558 |
> |
* @return {@code true} if all threads are currently idle |
1559 |
|
*/ |
1560 |
|
public boolean isQuiescent() { |
1561 |
< |
return activeCountOf(runControl) == 0; |
1561 |
> |
return (runState & ACTIVE_COUNT_MASK) == 0; |
1562 |
|
} |
1563 |
|
|
1564 |
|
/** |
1566 |
|
* one thread's work queue by another. The reported value |
1567 |
|
* underestimates the actual total number of steals when the pool |
1568 |
|
* is not quiescent. This value may be useful for monitoring and |
1569 |
< |
* tuning fork/join programs: In general, steal counts should be |
1569 |
> |
* tuning fork/join programs: in general, steal counts should be |
1570 |
|
* high enough to keep threads busy, but low enough to avoid |
1571 |
|
* overhead and contention across threads. |
1572 |
< |
* @return the number of steals. |
1572 |
> |
* |
1573 |
> |
* @return the number of steals |
1574 |
|
*/ |
1575 |
|
public long getStealCount() { |
1576 |
< |
return stealCount.get(); |
909 |
< |
} |
910 |
< |
|
911 |
< |
/** |
912 |
< |
* Accumulate steal count from a worker. Call only |
913 |
< |
* when worker known to be idle. |
914 |
< |
*/ |
915 |
< |
private void updateStealCount(ForkJoinWorkerThread w) { |
916 |
< |
int sc = w.getAndClearStealCount(); |
917 |
< |
if (sc != 0) |
918 |
< |
stealCount.addAndGet(sc); |
1576 |
> |
return stealCount; |
1577 |
|
} |
1578 |
|
|
1579 |
|
/** |
1583 |
|
* an approximation, obtained by iterating across all threads in |
1584 |
|
* the pool. This method may be useful for tuning task |
1585 |
|
* granularities. |
1586 |
< |
* @return the number of queued tasks. |
1586 |
> |
* |
1587 |
> |
* @return the number of queued tasks |
1588 |
|
*/ |
1589 |
|
public long getQueuedTaskCount() { |
1590 |
|
long count = 0; |
1591 |
|
ForkJoinWorkerThread[] ws = workers; |
1592 |
< |
if (ws != null) { |
1593 |
< |
for (int i = 0; i < ws.length; ++i) { |
1594 |
< |
ForkJoinWorkerThread t = ws[i]; |
1595 |
< |
if (t != null) |
1596 |
< |
count += t.getQueueSize(); |
938 |
< |
} |
1592 |
> |
int nws = ws.length; |
1593 |
> |
for (int i = 0; i < nws; ++i) { |
1594 |
> |
ForkJoinWorkerThread w = ws[i]; |
1595 |
> |
if (w != null) |
1596 |
> |
count += w.getQueueSize(); |
1597 |
|
} |
1598 |
|
return count; |
1599 |
|
} |
1600 |
|
|
1601 |
|
/** |
1602 |
< |
* Returns an estimate of the number tasks submitted to this pool |
1603 |
< |
* that have not yet begun executing. This method takes time |
1602 |
> |
* Returns an estimate of the number of tasks submitted to this |
1603 |
> |
* pool that have not yet begun executing. This method takes time |
1604 |
|
* proportional to the number of submissions. |
1605 |
< |
* @return the number of queued submissions. |
1605 |
> |
* |
1606 |
> |
* @return the number of queued submissions |
1607 |
|
*/ |
1608 |
|
public int getQueuedSubmissionCount() { |
1609 |
|
return submissionQueue.size(); |
1610 |
|
} |
1611 |
|
|
1612 |
|
/** |
1613 |
< |
* Returns true if there are any tasks submitted to this pool |
1614 |
< |
* that have not yet begun executing. |
1615 |
< |
* @return <code>true</code> if there are any queued submissions. |
1613 |
> |
* Returns {@code true} if there are any tasks submitted to this |
1614 |
> |
* pool that have not yet begun executing. |
1615 |
> |
* |
1616 |
> |
* @return {@code true} if there are any queued submissions |
1617 |
|
*/ |
1618 |
|
public boolean hasQueuedSubmissions() { |
1619 |
|
return !submissionQueue.isEmpty(); |
1623 |
|
* Removes and returns the next unexecuted submission if one is |
1624 |
|
* available. This method may be useful in extensions to this |
1625 |
|
* class that re-assign work in systems with multiple pools. |
1626 |
< |
* @return the next submission, or null if none |
1626 |
> |
* |
1627 |
> |
* @return the next submission, or {@code null} if none |
1628 |
|
*/ |
1629 |
|
protected ForkJoinTask<?> pollSubmission() { |
1630 |
|
return submissionQueue.poll(); |
1634 |
|
* Removes all available unexecuted submitted and forked tasks |
1635 |
|
* from scheduling queues and adds them to the given collection, |
1636 |
|
* without altering their execution status. These may include |
1637 |
< |
* artifically generated or wrapped tasks. This method id designed |
1638 |
< |
* to be invoked only when the pool is known to be |
1637 |
> |
* artificially generated or wrapped tasks. This method is |
1638 |
> |
* designed to be invoked only when the pool is known to be |
1639 |
|
* quiescent. Invocations at other times may not remove all |
1640 |
|
* tasks. A failure encountered while attempting to add elements |
1641 |
< |
* to collection <tt>c</tt> may result in elements being in |
1641 |
> |
* to collection {@code c} may result in elements being in |
1642 |
|
* neither, either or both collections when the associated |
1643 |
|
* exception is thrown. The behavior of this operation is |
1644 |
|
* undefined if the specified collection is modified while the |
1645 |
|
* operation is in progress. |
1646 |
+ |
* |
1647 |
|
* @param c the collection to transfer elements into |
1648 |
|
* @return the number of elements transferred |
1649 |
|
*/ |
1650 |
< |
protected int drainTasksTo(Collection<ForkJoinTask<?>> c) { |
1650 |
> |
protected int drainTasksTo(Collection<? super ForkJoinTask<?>> c) { |
1651 |
|
int n = submissionQueue.drainTo(c); |
1652 |
|
ForkJoinWorkerThread[] ws = workers; |
1653 |
< |
if (ws != null) { |
1654 |
< |
for (int i = 0; i < ws.length; ++i) { |
1655 |
< |
ForkJoinWorkerThread w = ws[i]; |
1656 |
< |
if (w != null) |
1657 |
< |
n += w.drainTasksTo(c); |
996 |
< |
} |
1653 |
> |
int nws = ws.length; |
1654 |
> |
for (int i = 0; i < nws; ++i) { |
1655 |
> |
ForkJoinWorkerThread w = ws[i]; |
1656 |
> |
if (w != null) |
1657 |
> |
n += w.drainTasksTo(c); |
1658 |
|
} |
1659 |
|
return n; |
1660 |
|
} |
1661 |
|
|
1662 |
|
/** |
1663 |
+ |
* Returns count of total parks by existing workers. |
1664 |
+ |
* Used during development only since not meaningful to users. |
1665 |
+ |
*/ |
1666 |
+ |
private int collectParkCount() { |
1667 |
+ |
int count = 0; |
1668 |
+ |
ForkJoinWorkerThread[] ws = workers; |
1669 |
+ |
int nws = ws.length; |
1670 |
+ |
for (int i = 0; i < nws; ++i) { |
1671 |
+ |
ForkJoinWorkerThread w = ws[i]; |
1672 |
+ |
if (w != null) |
1673 |
+ |
count += w.parkCount; |
1674 |
+ |
} |
1675 |
+ |
return count; |
1676 |
+ |
} |
1677 |
+ |
|
1678 |
+ |
/** |
1679 |
|
* Returns a string identifying this pool, as well as its state, |
1680 |
|
* including indications of run state, parallelism level, and |
1681 |
|
* worker and task counts. |
1683 |
|
* @return a string identifying this pool, as well as its state |
1684 |
|
*/ |
1685 |
|
public String toString() { |
1009 |
– |
int ps = parallelism; |
1010 |
– |
int wc = workerCounts; |
1011 |
– |
int rc = runControl; |
1686 |
|
long st = getStealCount(); |
1687 |
|
long qt = getQueuedTaskCount(); |
1688 |
|
long qs = getQueuedSubmissionCount(); |
1689 |
+ |
int wc = workerCounts; |
1690 |
+ |
int tc = wc >>> TOTAL_COUNT_SHIFT; |
1691 |
+ |
int rc = wc & RUNNING_COUNT_MASK; |
1692 |
+ |
int pc = parallelism; |
1693 |
+ |
int rs = runState; |
1694 |
+ |
int ac = rs & ACTIVE_COUNT_MASK; |
1695 |
+ |
// int pk = collectParkCount(); |
1696 |
|
return super.toString() + |
1697 |
< |
"[" + runStateToString(runStateOf(rc)) + |
1698 |
< |
", parallelism = " + ps + |
1699 |
< |
", size = " + totalCountOf(wc) + |
1700 |
< |
", active = " + activeCountOf(rc) + |
1701 |
< |
", running = " + runningCountOf(wc) + |
1697 |
> |
"[" + runLevelToString(rs) + |
1698 |
> |
", parallelism = " + pc + |
1699 |
> |
", size = " + tc + |
1700 |
> |
", active = " + ac + |
1701 |
> |
", running = " + rc + |
1702 |
|
", steals = " + st + |
1703 |
|
", tasks = " + qt + |
1704 |
|
", submissions = " + qs + |
1705 |
+ |
// ", parks = " + pk + |
1706 |
|
"]"; |
1707 |
|
} |
1708 |
|
|
1709 |
< |
private static String runStateToString(int rs) { |
1710 |
< |
switch(rs) { |
1711 |
< |
case RUNNING: return "Running"; |
1712 |
< |
case SHUTDOWN: return "Shutting down"; |
1713 |
< |
case TERMINATING: return "Terminating"; |
1032 |
< |
case TERMINATED: return "Terminated"; |
1033 |
< |
default: throw new Error("Unknown run state"); |
1034 |
< |
} |
1709 |
> |
private static String runLevelToString(int s) { |
1710 |
> |
return ((s & TERMINATED) != 0 ? "Terminated" : |
1711 |
> |
((s & TERMINATING) != 0 ? "Terminating" : |
1712 |
> |
((s & SHUTDOWN) != 0 ? "Shutting down" : |
1713 |
> |
"Running"))); |
1714 |
|
} |
1715 |
|
|
1037 |
– |
// lifecycle control |
1038 |
– |
|
1716 |
|
/** |
1717 |
|
* Initiates an orderly shutdown in which previously submitted |
1718 |
|
* tasks are executed, but no new tasks will be accepted. |
1719 |
|
* Invocation has no additional effect if already shut down. |
1720 |
|
* Tasks that are in the process of being submitted concurrently |
1721 |
|
* during the course of this method may or may not be rejected. |
1722 |
+ |
* |
1723 |
|
* @throws SecurityException if a security manager exists and |
1724 |
|
* the caller is not permitted to modify threads |
1725 |
|
* because it does not hold {@link |
1726 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1726 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1727 |
|
*/ |
1728 |
|
public void shutdown() { |
1729 |
|
checkPermission(); |
1730 |
< |
transitionRunStateTo(SHUTDOWN); |
1731 |
< |
if (canTerminateOnShutdown(runControl)) |
1054 |
< |
terminateOnShutdown(); |
1730 |
> |
advanceRunLevel(SHUTDOWN); |
1731 |
> |
tryTerminate(false); |
1732 |
|
} |
1733 |
|
|
1734 |
|
/** |
1735 |
< |
* Attempts to stop all actively executing tasks, and cancels all |
1736 |
< |
* waiting tasks. Tasks that are in the process of being |
1737 |
< |
* submitted or executed concurrently during the course of this |
1738 |
< |
* method may or may not be rejected. Unlike some other executors, |
1739 |
< |
* this method cancels rather than collects non-executed tasks |
1740 |
< |
* upon termination, so always returns an empty list. However, you |
1741 |
< |
* can use method <code>drainTasksTo</code> before invoking this |
1742 |
< |
* method to transfer unexecuted tasks to another collection. |
1735 |
> |
* Attempts to cancel and/or stop all tasks, and reject all |
1736 |
> |
* subsequently submitted tasks. Tasks that are in the process of |
1737 |
> |
* being submitted or executed concurrently during the course of |
1738 |
> |
* this method may or may not be rejected. This method cancels |
1739 |
> |
* both existing and unexecuted tasks, in order to permit |
1740 |
> |
* termination in the presence of task dependencies. So the method |
1741 |
> |
* always returns an empty list (unlike the case for some other |
1742 |
> |
* Executors). |
1743 |
> |
* |
1744 |
|
* @return an empty list |
1745 |
|
* @throws SecurityException if a security manager exists and |
1746 |
|
* the caller is not permitted to modify threads |
1747 |
|
* because it does not hold {@link |
1748 |
< |
* java.lang.RuntimePermission}<code>("modifyThread")</code>, |
1748 |
> |
* java.lang.RuntimePermission}{@code ("modifyThread")} |
1749 |
|
*/ |
1750 |
|
public List<Runnable> shutdownNow() { |
1751 |
|
checkPermission(); |
1752 |
< |
terminate(); |
1752 |
> |
tryTerminate(true); |
1753 |
|
return Collections.emptyList(); |
1754 |
|
} |
1755 |
|
|
1756 |
|
/** |
1757 |
< |
* Returns <code>true</code> if all tasks have completed following shut down. |
1757 |
> |
* Returns {@code true} if all tasks have completed following shut down. |
1758 |
|
* |
1759 |
< |
* @return <code>true</code> if all tasks have completed following shut down |
1759 |
> |
* @return {@code true} if all tasks have completed following shut down |
1760 |
|
*/ |
1761 |
|
public boolean isTerminated() { |
1762 |
< |
return runStateOf(runControl) == TERMINATED; |
1762 |
> |
return runState >= TERMINATED; |
1763 |
|
} |
1764 |
|
|
1765 |
|
/** |
1766 |
< |
* Returns <code>true</code> if the process of termination has |
1767 |
< |
* commenced but possibly not yet completed. |
1766 |
> |
* Returns {@code true} if the process of termination has |
1767 |
> |
* commenced but not yet completed. This method may be useful for |
1768 |
> |
* debugging. A return of {@code true} reported a sufficient |
1769 |
> |
* period after shutdown may indicate that submitted tasks have |
1770 |
> |
* ignored or suppressed interruption, causing this executor not |
1771 |
> |
* to properly terminate. |
1772 |
|
* |
1773 |
< |
* @return <code>true</code> if terminating |
1773 |
> |
* @return {@code true} if terminating but not yet terminated |
1774 |
|
*/ |
1775 |
|
public boolean isTerminating() { |
1776 |
< |
return runStateOf(runControl) >= TERMINATING; |
1776 |
> |
return (runState & (TERMINATING|TERMINATED)) == TERMINATING; |
1777 |
|
} |
1778 |
|
|
1779 |
|
/** |
1780 |
< |
* Returns <code>true</code> if this pool has been shut down. |
1780 |
> |
* Returns {@code true} if this pool has been shut down. |
1781 |
|
* |
1782 |
< |
* @return <code>true</code> if this pool has been shut down |
1782 |
> |
* @return {@code true} if this pool has been shut down |
1783 |
|
*/ |
1784 |
|
public boolean isShutdown() { |
1785 |
< |
return runStateOf(runControl) >= SHUTDOWN; |
1785 |
> |
return runState >= SHUTDOWN; |
1786 |
|
} |
1787 |
|
|
1788 |
|
/** |
1792 |
|
* |
1793 |
|
* @param timeout the maximum time to wait |
1794 |
|
* @param unit the time unit of the timeout argument |
1795 |
< |
* @return <code>true</code> if this executor terminated and |
1796 |
< |
* <code>false</code> if the timeout elapsed before termination |
1795 |
> |
* @return {@code true} if this executor terminated and |
1796 |
> |
* {@code false} if the timeout elapsed before termination |
1797 |
|
* @throws InterruptedException if interrupted while waiting |
1798 |
|
*/ |
1799 |
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1800 |
|
throws InterruptedException { |
1119 |
– |
long nanos = unit.toNanos(timeout); |
1120 |
– |
final ReentrantLock lock = this.workerLock; |
1121 |
– |
lock.lock(); |
1801 |
|
try { |
1802 |
< |
for (;;) { |
1803 |
< |
if (isTerminated()) |
1125 |
< |
return true; |
1126 |
< |
if (nanos <= 0) |
1127 |
< |
return false; |
1128 |
< |
nanos = termination.awaitNanos(nanos); |
1129 |
< |
} |
1130 |
< |
} finally { |
1131 |
< |
lock.unlock(); |
1132 |
< |
} |
1133 |
< |
} |
1134 |
< |
|
1135 |
< |
// Shutdown and termination support |
1136 |
< |
|
1137 |
< |
/** |
1138 |
< |
* Callback from terminating worker. Null out the corresponding |
1139 |
< |
* workers slot, and if terminating, try to terminate, else try to |
1140 |
< |
* shrink workers array. |
1141 |
< |
* @param w the worker |
1142 |
< |
*/ |
1143 |
< |
final void workerTerminated(ForkJoinWorkerThread w) { |
1144 |
< |
updateStealCount(w); |
1145 |
< |
updateWorkerCount(-1); |
1146 |
< |
final ReentrantLock lock = this.workerLock; |
1147 |
< |
lock.lock(); |
1148 |
< |
try { |
1149 |
< |
ForkJoinWorkerThread[] ws = workers; |
1150 |
< |
if (ws != null) { |
1151 |
< |
int idx = w.poolIndex; |
1152 |
< |
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1153 |
< |
ws[idx] = null; |
1154 |
< |
if (totalCountOf(workerCounts) == 0) { |
1155 |
< |
terminate(); // no-op if already terminating |
1156 |
< |
transitionRunStateTo(TERMINATED); |
1157 |
< |
termination.signalAll(); |
1158 |
< |
} |
1159 |
< |
else if (!isTerminating()) { |
1160 |
< |
tryShrinkWorkerArray(); |
1161 |
< |
tryResumeSpare(true); // allow replacement |
1162 |
< |
} |
1163 |
< |
} |
1164 |
< |
} finally { |
1165 |
< |
lock.unlock(); |
1166 |
< |
} |
1167 |
< |
signalIdleWorkers(); |
1168 |
< |
} |
1169 |
< |
|
1170 |
< |
/** |
1171 |
< |
* Initiate termination. |
1172 |
< |
*/ |
1173 |
< |
private void terminate() { |
1174 |
< |
if (transitionRunStateTo(TERMINATING)) { |
1175 |
< |
stopAllWorkers(); |
1176 |
< |
resumeAllSpares(); |
1177 |
< |
signalIdleWorkers(); |
1178 |
< |
cancelQueuedSubmissions(); |
1179 |
< |
cancelQueuedWorkerTasks(); |
1180 |
< |
interruptUnterminatedWorkers(); |
1181 |
< |
signalIdleWorkers(); // resignal after interrupt |
1182 |
< |
} |
1183 |
< |
} |
1184 |
< |
|
1185 |
< |
/** |
1186 |
< |
* Possibly terminate when on shutdown state |
1187 |
< |
*/ |
1188 |
< |
private void terminateOnShutdown() { |
1189 |
< |
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1190 |
< |
terminate(); |
1191 |
< |
} |
1192 |
< |
|
1193 |
< |
/** |
1194 |
< |
* Clear out and cancel submissions |
1195 |
< |
*/ |
1196 |
< |
private void cancelQueuedSubmissions() { |
1197 |
< |
ForkJoinTask<?> task; |
1198 |
< |
while ((task = pollSubmission()) != null) |
1199 |
< |
task.cancel(false); |
1200 |
< |
} |
1201 |
< |
|
1202 |
< |
/** |
1203 |
< |
* Clean out worker queues. |
1204 |
< |
*/ |
1205 |
< |
private void cancelQueuedWorkerTasks() { |
1206 |
< |
final ReentrantLock lock = this.workerLock; |
1207 |
< |
lock.lock(); |
1208 |
< |
try { |
1209 |
< |
ForkJoinWorkerThread[] ws = workers; |
1210 |
< |
if (ws != null) { |
1211 |
< |
for (int i = 0; i < ws.length; ++i) { |
1212 |
< |
ForkJoinWorkerThread t = ws[i]; |
1213 |
< |
if (t != null) |
1214 |
< |
t.cancelTasks(); |
1215 |
< |
} |
1216 |
< |
} |
1217 |
< |
} finally { |
1218 |
< |
lock.unlock(); |
1219 |
< |
} |
1220 |
< |
} |
1221 |
< |
|
1222 |
< |
/** |
1223 |
< |
* Set each worker's status to terminating. Requires lock to avoid |
1224 |
< |
* conflicts with add/remove |
1225 |
< |
*/ |
1226 |
< |
private void stopAllWorkers() { |
1227 |
< |
final ReentrantLock lock = this.workerLock; |
1228 |
< |
lock.lock(); |
1229 |
< |
try { |
1230 |
< |
ForkJoinWorkerThread[] ws = workers; |
1231 |
< |
if (ws != null) { |
1232 |
< |
for (int i = 0; i < ws.length; ++i) { |
1233 |
< |
ForkJoinWorkerThread t = ws[i]; |
1234 |
< |
if (t != null) |
1235 |
< |
t.shutdownNow(); |
1236 |
< |
} |
1237 |
< |
} |
1238 |
< |
} finally { |
1239 |
< |
lock.unlock(); |
1240 |
< |
} |
1241 |
< |
} |
1242 |
< |
|
1243 |
< |
/** |
1244 |
< |
* Interrupt all unterminated workers. This is not required for |
1245 |
< |
* sake of internal control, but may help unstick user code during |
1246 |
< |
* shutdown. |
1247 |
< |
*/ |
1248 |
< |
private void interruptUnterminatedWorkers() { |
1249 |
< |
final ReentrantLock lock = this.workerLock; |
1250 |
< |
lock.lock(); |
1251 |
< |
try { |
1252 |
< |
ForkJoinWorkerThread[] ws = workers; |
1253 |
< |
if (ws != null) { |
1254 |
< |
for (int i = 0; i < ws.length; ++i) { |
1255 |
< |
ForkJoinWorkerThread t = ws[i]; |
1256 |
< |
if (t != null && !t.isTerminated()) { |
1257 |
< |
try { |
1258 |
< |
t.interrupt(); |
1259 |
< |
} catch (SecurityException ignore) { |
1260 |
< |
} |
1261 |
< |
} |
1262 |
< |
} |
1263 |
< |
} |
1264 |
< |
} finally { |
1265 |
< |
lock.unlock(); |
1266 |
< |
} |
1267 |
< |
} |
1268 |
< |
|
1269 |
< |
|
1270 |
< |
/* |
1271 |
< |
* Nodes for event barrier to manage idle threads. Queue nodes |
1272 |
< |
* are basic Treiber stack nodes, also used for spare stack. |
1273 |
< |
* |
1274 |
< |
* The event barrier has an event count and a wait queue (actually |
1275 |
< |
* a Treiber stack). Workers are enabled to look for work when |
1276 |
< |
* the eventCount is incremented. If they fail to find work, they |
1277 |
< |
* may wait for next count. Upon release, threads help others wake |
1278 |
< |
* up. |
1279 |
< |
* |
1280 |
< |
* Synchronization events occur only in enough contexts to |
1281 |
< |
* maintain overall liveness: |
1282 |
< |
* |
1283 |
< |
* - Submission of a new task to the pool |
1284 |
< |
* - Resizes or other changes to the workers array |
1285 |
< |
* - pool termination |
1286 |
< |
* - A worker pushing a task on an empty queue |
1287 |
< |
* |
1288 |
< |
* The case of pushing a task occurs often enough, and is heavy |
1289 |
< |
* enough compared to simple stack pushes, to require special |
1290 |
< |
* handling: Method signalWork returns without advancing count if |
1291 |
< |
* the queue appears to be empty. This would ordinarily result in |
1292 |
< |
* races causing some queued waiters not to be woken up. To avoid |
1293 |
< |
* this, the first worker enqueued in method sync (see |
1294 |
< |
* syncIsReleasable) rescans for tasks after being enqueued, and |
1295 |
< |
* helps signal if any are found. This works well because the |
1296 |
< |
* worker has nothing better to do, and so might as well help |
1297 |
< |
* alleviate the overhead and contention on the threads actually |
1298 |
< |
* doing work. Also, since event counts increments on task |
1299 |
< |
* availability exist to maintain liveness (rather than to force |
1300 |
< |
* refreshes etc), it is OK for callers to exit early if |
1301 |
< |
* contending with another signaller. |
1302 |
< |
*/ |
1303 |
< |
static final class WaitQueueNode { |
1304 |
< |
WaitQueueNode next; // only written before enqueued |
1305 |
< |
volatile ForkJoinWorkerThread thread; // nulled to cancel wait |
1306 |
< |
final long count; // unused for spare stack |
1307 |
< |
|
1308 |
< |
WaitQueueNode(long c, ForkJoinWorkerThread w) { |
1309 |
< |
count = c; |
1310 |
< |
thread = w; |
1311 |
< |
} |
1312 |
< |
|
1313 |
< |
/** |
1314 |
< |
* Wake up waiter, returning false if known to already |
1315 |
< |
*/ |
1316 |
< |
boolean signal() { |
1317 |
< |
ForkJoinWorkerThread t = thread; |
1318 |
< |
if (t == null) |
1319 |
< |
return false; |
1320 |
< |
thread = null; |
1321 |
< |
LockSupport.unpark(t); |
1322 |
< |
return true; |
1323 |
< |
} |
1324 |
< |
|
1325 |
< |
/** |
1326 |
< |
* Await release on sync |
1327 |
< |
*/ |
1328 |
< |
void awaitSyncRelease(ForkJoinPool p) { |
1329 |
< |
while (thread != null && !p.syncIsReleasable(this)) |
1330 |
< |
LockSupport.park(this); |
1331 |
< |
} |
1332 |
< |
|
1333 |
< |
/** |
1334 |
< |
* Await resumption as spare |
1335 |
< |
*/ |
1336 |
< |
void awaitSpareRelease() { |
1337 |
< |
while (thread != null) { |
1338 |
< |
if (!Thread.interrupted()) |
1339 |
< |
LockSupport.park(this); |
1340 |
< |
} |
1341 |
< |
} |
1342 |
< |
} |
1343 |
< |
|
1344 |
< |
/** |
1345 |
< |
* Ensures that no thread is waiting for count to advance from the |
1346 |
< |
* current value of eventCount read on entry to this method, by |
1347 |
< |
* releasing waiting threads if necessary. |
1348 |
< |
* @return the count |
1349 |
< |
*/ |
1350 |
< |
final long ensureSync() { |
1351 |
< |
long c = eventCount; |
1352 |
< |
WaitQueueNode q; |
1353 |
< |
while ((q = syncStack) != null && q.count < c) { |
1354 |
< |
if (casBarrierStack(q, null)) { |
1355 |
< |
do { |
1356 |
< |
q.signal(); |
1357 |
< |
} while ((q = q.next) != null); |
1358 |
< |
break; |
1359 |
< |
} |
1360 |
< |
} |
1361 |
< |
return c; |
1362 |
< |
} |
1363 |
< |
|
1364 |
< |
/** |
1365 |
< |
* Increments event count and releases waiting threads. |
1366 |
< |
*/ |
1367 |
< |
private void signalIdleWorkers() { |
1368 |
< |
long c; |
1369 |
< |
do;while (!casEventCount(c = eventCount, c+1)); |
1370 |
< |
ensureSync(); |
1371 |
< |
} |
1372 |
< |
|
1373 |
< |
/** |
1374 |
< |
* Signal threads waiting to poll a task. Because method sync |
1375 |
< |
* rechecks availability, it is OK to only proceed if queue |
1376 |
< |
* appears to be non-empty, and OK to skip under contention to |
1377 |
< |
* increment count (since some other thread succeeded). |
1378 |
< |
*/ |
1379 |
< |
final void signalWork() { |
1380 |
< |
long c; |
1381 |
< |
WaitQueueNode q; |
1382 |
< |
if (syncStack != null && |
1383 |
< |
casEventCount(c = eventCount, c+1) && |
1384 |
< |
(((q = syncStack) != null && q.count <= c) && |
1385 |
< |
(!casBarrierStack(q, q.next) || !q.signal()))) |
1386 |
< |
ensureSync(); |
1387 |
< |
} |
1388 |
< |
|
1389 |
< |
/** |
1390 |
< |
* Waits until event count advances from last value held by |
1391 |
< |
* caller, or if excess threads, caller is resumed as spare, or |
1392 |
< |
* caller or pool is terminating. Updates caller's event on exit. |
1393 |
< |
* @param w the calling worker thread |
1394 |
< |
*/ |
1395 |
< |
final void sync(ForkJoinWorkerThread w) { |
1396 |
< |
updateStealCount(w); // Transfer w's count while it is idle |
1397 |
< |
|
1398 |
< |
while (!w.isShutdown() && !isTerminating() && !suspendIfSpare(w)) { |
1399 |
< |
long prev = w.lastEventCount; |
1400 |
< |
WaitQueueNode node = null; |
1401 |
< |
WaitQueueNode h; |
1402 |
< |
while (eventCount == prev && |
1403 |
< |
((h = syncStack) == null || h.count == prev)) { |
1404 |
< |
if (node == null) |
1405 |
< |
node = new WaitQueueNode(prev, w); |
1406 |
< |
if (casBarrierStack(node.next = h, node)) { |
1407 |
< |
node.awaitSyncRelease(this); |
1408 |
< |
break; |
1409 |
< |
} |
1410 |
< |
} |
1411 |
< |
long ec = ensureSync(); |
1412 |
< |
if (ec != prev) { |
1413 |
< |
w.lastEventCount = ec; |
1414 |
< |
break; |
1415 |
< |
} |
1416 |
< |
} |
1417 |
< |
} |
1418 |
< |
|
1419 |
< |
/** |
1420 |
< |
* Returns true if worker waiting on sync can proceed: |
1421 |
< |
* - on signal (thread == null) |
1422 |
< |
* - on event count advance (winning race to notify vs signaller) |
1423 |
< |
* - on Interrupt |
1424 |
< |
* - if the first queued node, we find work available |
1425 |
< |
* If node was not signalled and event count not advanced on exit, |
1426 |
< |
* then we also help advance event count. |
1427 |
< |
* @return true if node can be released |
1428 |
< |
*/ |
1429 |
< |
final boolean syncIsReleasable(WaitQueueNode node) { |
1430 |
< |
long prev = node.count; |
1431 |
< |
if (!Thread.interrupted() && node.thread != null && |
1432 |
< |
(node.next != null || |
1433 |
< |
!ForkJoinWorkerThread.hasQueuedTasks(workers)) && |
1434 |
< |
eventCount == prev) |
1802 |
> |
return termination.awaitAdvanceInterruptibly(0, timeout, unit) > 0; |
1803 |
> |
} catch(TimeoutException ex) { |
1804 |
|
return false; |
1436 |
– |
if (node.thread != null) { |
1437 |
– |
node.thread = null; |
1438 |
– |
long ec = eventCount; |
1439 |
– |
if (prev <= ec) // help signal |
1440 |
– |
casEventCount(ec, ec+1); |
1441 |
– |
} |
1442 |
– |
return true; |
1443 |
– |
} |
1444 |
– |
|
1445 |
– |
/** |
1446 |
– |
* Returns true if a new sync event occurred since last call to |
1447 |
– |
* sync or this method, if so, updating caller's count. |
1448 |
– |
*/ |
1449 |
– |
final boolean hasNewSyncEvent(ForkJoinWorkerThread w) { |
1450 |
– |
long lc = w.lastEventCount; |
1451 |
– |
long ec = ensureSync(); |
1452 |
– |
if (ec == lc) |
1453 |
– |
return false; |
1454 |
– |
w.lastEventCount = ec; |
1455 |
– |
return true; |
1456 |
– |
} |
1457 |
– |
|
1458 |
– |
// Parallelism maintenance |
1459 |
– |
|
1460 |
– |
/** |
1461 |
– |
* Decrement running count; if too low, add spare. |
1462 |
– |
* |
1463 |
– |
* Conceptually, all we need to do here is add or resume a |
1464 |
– |
* spare thread when one is about to block (and remove or |
1465 |
– |
* suspend it later when unblocked -- see suspendIfSpare). |
1466 |
– |
* However, implementing this idea requires coping with |
1467 |
– |
* several problems: We have imperfect information about the |
1468 |
– |
* states of threads. Some count updates can and usually do |
1469 |
– |
* lag run state changes, despite arrangements to keep them |
1470 |
– |
* accurate (for example, when possible, updating counts |
1471 |
– |
* before signalling or resuming), especially when running on |
1472 |
– |
* dynamic JVMs that don't optimize the infrequent paths that |
1473 |
– |
* update counts. Generating too many threads can make these |
1474 |
– |
* problems become worse, because excess threads are more |
1475 |
– |
* likely to be context-switched with others, slowing them all |
1476 |
– |
* down, especially if there is no work available, so all are |
1477 |
– |
* busy scanning or idling. Also, excess spare threads can |
1478 |
– |
* only be suspended or removed when they are idle, not |
1479 |
– |
* immediately when they aren't needed. So adding threads will |
1480 |
– |
* raise parallelism level for longer than necessary. Also, |
1481 |
– |
* FJ applications often enounter highly transient peaks when |
1482 |
– |
* many threads are blocked joining, but for less time than it |
1483 |
– |
* takes to create or resume spares. |
1484 |
– |
* |
1485 |
– |
* @param joinMe if non-null, return early if done |
1486 |
– |
* @param maintainParallelism if true, try to stay within |
1487 |
– |
* target counts, else create only to avoid starvation |
1488 |
– |
* @return true if joinMe known to be done |
1489 |
– |
*/ |
1490 |
– |
final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) { |
1491 |
– |
maintainParallelism &= maintainsParallelism; // overrride |
1492 |
– |
boolean dec = false; // true when running count decremented |
1493 |
– |
while (spareStack == null || !tryResumeSpare(dec)) { |
1494 |
– |
int counts = workerCounts; |
1495 |
– |
if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat |
1496 |
– |
if (!needSpare(counts, maintainParallelism)) |
1497 |
– |
break; |
1498 |
– |
if (joinMe.status < 0) |
1499 |
– |
return true; |
1500 |
– |
if (tryAddSpare(counts)) |
1501 |
– |
break; |
1502 |
– |
} |
1503 |
– |
} |
1504 |
– |
return false; |
1505 |
– |
} |
1506 |
– |
|
1507 |
– |
/** |
1508 |
– |
* Same idea as preJoin |
1509 |
– |
*/ |
1510 |
– |
final boolean preBlock(ManagedBlocker blocker, |
1511 |
– |
boolean maintainParallelism) { |
1512 |
– |
maintainParallelism &= maintainsParallelism; |
1513 |
– |
boolean dec = false; |
1514 |
– |
while (spareStack == null || !tryResumeSpare(dec)) { |
1515 |
– |
int counts = workerCounts; |
1516 |
– |
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1517 |
– |
if (!needSpare(counts, maintainParallelism)) |
1518 |
– |
break; |
1519 |
– |
if (blocker.isReleasable()) |
1520 |
– |
return true; |
1521 |
– |
if (tryAddSpare(counts)) |
1522 |
– |
break; |
1523 |
– |
} |
1524 |
– |
} |
1525 |
– |
return false; |
1526 |
– |
} |
1527 |
– |
|
1528 |
– |
/** |
1529 |
– |
* Returns true if a spare thread appears to be needed. If |
1530 |
– |
* maintaining parallelism, returns true when the deficit in |
1531 |
– |
* running threads is more than the surplus of total threads, and |
1532 |
– |
* there is apparently some work to do. This self-limiting rule |
1533 |
– |
* means that the more threads that have already been added, the |
1534 |
– |
* less parallelism we will tolerate before adding another. |
1535 |
– |
* @param counts current worker counts |
1536 |
– |
* @param maintainParallelism try to maintain parallelism |
1537 |
– |
*/ |
1538 |
– |
private boolean needSpare(int counts, boolean maintainParallelism) { |
1539 |
– |
int ps = parallelism; |
1540 |
– |
int rc = runningCountOf(counts); |
1541 |
– |
int tc = totalCountOf(counts); |
1542 |
– |
int runningDeficit = ps - rc; |
1543 |
– |
int totalSurplus = tc - ps; |
1544 |
– |
return (tc < maxPoolSize && |
1545 |
– |
(rc == 0 || totalSurplus < 0 || |
1546 |
– |
(maintainParallelism && |
1547 |
– |
runningDeficit > totalSurplus && |
1548 |
– |
ForkJoinWorkerThread.hasQueuedTasks(workers)))); |
1549 |
– |
} |
1550 |
– |
|
1551 |
– |
/** |
1552 |
– |
* Add a spare worker if lock available and no more than the |
1553 |
– |
* expected numbers of threads exist |
1554 |
– |
* @return true if successful |
1555 |
– |
*/ |
1556 |
– |
private boolean tryAddSpare(int expectedCounts) { |
1557 |
– |
final ReentrantLock lock = this.workerLock; |
1558 |
– |
int expectedRunning = runningCountOf(expectedCounts); |
1559 |
– |
int expectedTotal = totalCountOf(expectedCounts); |
1560 |
– |
boolean success = false; |
1561 |
– |
boolean locked = false; |
1562 |
– |
// confirm counts while locking; CAS after obtaining lock |
1563 |
– |
try { |
1564 |
– |
for (;;) { |
1565 |
– |
int s = workerCounts; |
1566 |
– |
int tc = totalCountOf(s); |
1567 |
– |
int rc = runningCountOf(s); |
1568 |
– |
if (rc > expectedRunning || tc > expectedTotal) |
1569 |
– |
break; |
1570 |
– |
if (!locked && !(locked = lock.tryLock())) |
1571 |
– |
break; |
1572 |
– |
if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) { |
1573 |
– |
createAndStartSpare(tc); |
1574 |
– |
success = true; |
1575 |
– |
break; |
1576 |
– |
} |
1577 |
– |
} |
1578 |
– |
} finally { |
1579 |
– |
if (locked) |
1580 |
– |
lock.unlock(); |
1581 |
– |
} |
1582 |
– |
return success; |
1583 |
– |
} |
1584 |
– |
|
1585 |
– |
/** |
1586 |
– |
* Add the kth spare worker. On entry, pool coounts are already |
1587 |
– |
* adjusted to reflect addition. |
1588 |
– |
*/ |
1589 |
– |
private void createAndStartSpare(int k) { |
1590 |
– |
ForkJoinWorkerThread w = null; |
1591 |
– |
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1); |
1592 |
– |
int len = ws.length; |
1593 |
– |
// Probably, we can place at slot k. If not, find empty slot |
1594 |
– |
if (k < len && ws[k] != null) { |
1595 |
– |
for (k = 0; k < len && ws[k] != null; ++k) |
1596 |
– |
; |
1597 |
– |
} |
1598 |
– |
if (k < len && !isTerminating() && (w = createWorker(k)) != null) { |
1599 |
– |
ws[k] = w; |
1600 |
– |
w.start(); |
1601 |
– |
} |
1602 |
– |
else |
1603 |
– |
updateWorkerCount(-1); // adjust on failure |
1604 |
– |
signalIdleWorkers(); |
1605 |
– |
} |
1606 |
– |
|
1607 |
– |
/** |
1608 |
– |
* Suspend calling thread w if there are excess threads. Called |
1609 |
– |
* only from sync. Spares are enqueued in a Treiber stack |
1610 |
– |
* using the same WaitQueueNodes as barriers. They are resumed |
1611 |
– |
* mainly in preJoin, but are also woken on pool events that |
1612 |
– |
* require all threads to check run state. |
1613 |
– |
* @param w the caller |
1614 |
– |
*/ |
1615 |
– |
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1616 |
– |
WaitQueueNode node = null; |
1617 |
– |
int s; |
1618 |
– |
while (parallelism < runningCountOf(s = workerCounts)) { |
1619 |
– |
if (node == null) |
1620 |
– |
node = new WaitQueueNode(0, w); |
1621 |
– |
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1622 |
– |
// push onto stack |
1623 |
– |
do;while (!casSpareStack(node.next = spareStack, node)); |
1624 |
– |
// block until released by resumeSpare |
1625 |
– |
node.awaitSpareRelease(); |
1626 |
– |
return true; |
1627 |
– |
} |
1628 |
– |
} |
1629 |
– |
return false; |
1630 |
– |
} |
1631 |
– |
|
1632 |
– |
/** |
1633 |
– |
* Try to pop and resume a spare thread. |
1634 |
– |
* @param updateCount if true, increment running count on success |
1635 |
– |
* @return true if successful |
1636 |
– |
*/ |
1637 |
– |
private boolean tryResumeSpare(boolean updateCount) { |
1638 |
– |
WaitQueueNode q; |
1639 |
– |
while ((q = spareStack) != null) { |
1640 |
– |
if (casSpareStack(q, q.next)) { |
1641 |
– |
if (updateCount) |
1642 |
– |
updateRunningCount(1); |
1643 |
– |
q.signal(); |
1644 |
– |
return true; |
1645 |
– |
} |
1646 |
– |
} |
1647 |
– |
return false; |
1648 |
– |
} |
1649 |
– |
|
1650 |
– |
/** |
1651 |
– |
* Pop and resume all spare threads. Same idea as ensureSync. |
1652 |
– |
* @return true if any spares released |
1653 |
– |
*/ |
1654 |
– |
private boolean resumeAllSpares() { |
1655 |
– |
WaitQueueNode q; |
1656 |
– |
while ( (q = spareStack) != null) { |
1657 |
– |
if (casSpareStack(q, null)) { |
1658 |
– |
do { |
1659 |
– |
updateRunningCount(1); |
1660 |
– |
q.signal(); |
1661 |
– |
} while ((q = q.next) != null); |
1662 |
– |
return true; |
1663 |
– |
} |
1664 |
– |
} |
1665 |
– |
return false; |
1666 |
– |
} |
1667 |
– |
|
1668 |
– |
/** |
1669 |
– |
* Pop and shutdown excessive spare threads. Call only while |
1670 |
– |
* holding lock. This is not guaranteed to eliminate all excess |
1671 |
– |
* threads, only those suspended as spares, which are the ones |
1672 |
– |
* unlikely to be needed in the future. |
1673 |
– |
*/ |
1674 |
– |
private void trimSpares() { |
1675 |
– |
int surplus = totalCountOf(workerCounts) - parallelism; |
1676 |
– |
WaitQueueNode q; |
1677 |
– |
while (surplus > 0 && (q = spareStack) != null) { |
1678 |
– |
if (casSpareStack(q, null)) { |
1679 |
– |
do { |
1680 |
– |
updateRunningCount(1); |
1681 |
– |
ForkJoinWorkerThread w = q.thread; |
1682 |
– |
if (w != null && surplus > 0 && |
1683 |
– |
runningCountOf(workerCounts) > 0 && w.shutdown()) |
1684 |
– |
--surplus; |
1685 |
– |
q.signal(); |
1686 |
– |
} while ((q = q.next) != null); |
1687 |
– |
} |
1805 |
|
} |
1806 |
|
} |
1807 |
|
|
1808 |
|
/** |
1809 |
|
* Interface for extending managed parallelism for tasks running |
1810 |
< |
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1811 |
< |
* Method <code>isReleasable</code> must return true if blocking is not |
1812 |
< |
* necessary. Method <code>block</code> blocks the current thread |
1813 |
< |
* if necessary (perhaps internally invoking isReleasable before |
1814 |
< |
* actually blocking.). |
1810 |
> |
* in {@link ForkJoinPool}s. |
1811 |
> |
* |
1812 |
> |
* <p>A {@code ManagedBlocker} provides two methods. |
1813 |
> |
* Method {@code isReleasable} must return {@code true} if |
1814 |
> |
* blocking is not necessary. Method {@code block} blocks the |
1815 |
> |
* current thread if necessary (perhaps internally invoking |
1816 |
> |
* {@code isReleasable} before actually blocking). |
1817 |
> |
* |
1818 |
|
* <p>For example, here is a ManagedBlocker based on a |
1819 |
|
* ReentrantLock: |
1820 |
< |
* <pre> |
1821 |
< |
* class ManagedLocker implements ManagedBlocker { |
1822 |
< |
* final ReentrantLock lock; |
1823 |
< |
* boolean hasLock = false; |
1824 |
< |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1825 |
< |
* public boolean block() { |
1826 |
< |
* if (!hasLock) |
1827 |
< |
* lock.lock(); |
1828 |
< |
* return true; |
1829 |
< |
* } |
1830 |
< |
* public boolean isReleasable() { |
1831 |
< |
* return hasLock || (hasLock = lock.tryLock()); |
1712 |
< |
* } |
1820 |
> |
* <pre> {@code |
1821 |
> |
* class ManagedLocker implements ManagedBlocker { |
1822 |
> |
* final ReentrantLock lock; |
1823 |
> |
* boolean hasLock = false; |
1824 |
> |
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1825 |
> |
* public boolean block() { |
1826 |
> |
* if (!hasLock) |
1827 |
> |
* lock.lock(); |
1828 |
> |
* return true; |
1829 |
> |
* } |
1830 |
> |
* public boolean isReleasable() { |
1831 |
> |
* return hasLock || (hasLock = lock.tryLock()); |
1832 |
|
* } |
1833 |
< |
* </pre> |
1833 |
> |
* }}</pre> |
1834 |
|
*/ |
1835 |
|
public static interface ManagedBlocker { |
1836 |
|
/** |
1837 |
|
* Possibly blocks the current thread, for example waiting for |
1838 |
|
* a lock or condition. |
1839 |
< |
* @return true if no additional blocking is necessary (i.e., |
1840 |
< |
* if isReleasable would return true). |
1839 |
> |
* |
1840 |
> |
* @return {@code true} if no additional blocking is necessary |
1841 |
> |
* (i.e., if isReleasable would return true) |
1842 |
|
* @throws InterruptedException if interrupted while waiting |
1843 |
< |
* (the method is not required to do so, but is allowe to). |
1843 |
> |
* (the method is not required to do so, but is allowed to) |
1844 |
|
*/ |
1845 |
|
boolean block() throws InterruptedException; |
1846 |
|
|
1847 |
|
/** |
1848 |
< |
* Returns true if blocking is unnecessary. |
1848 |
> |
* Returns {@code true} if blocking is unnecessary. |
1849 |
|
*/ |
1850 |
|
boolean isReleasable(); |
1851 |
|
} |
1852 |
|
|
1853 |
|
/** |
1854 |
|
* Blocks in accord with the given blocker. If the current thread |
1855 |
< |
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1856 |
< |
* spare thread to be activated if necessary to ensure parallelism |
1857 |
< |
* while the current thread is blocked. If |
1858 |
< |
* <code>maintainParallelism</code> is true and the pool supports |
1859 |
< |
* it ({@link #getMaintainsParallelism}), this method attempts to |
1860 |
< |
* maintain the pool's nominal parallelism. Otherwise if activates |
1861 |
< |
* a thread only if necessary to avoid complete starvation. This |
1862 |
< |
* option may be preferable when blockages use timeouts, or are |
1863 |
< |
* almost always brief. |
1864 |
< |
* |
1865 |
< |
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
1866 |
< |
* equivalent to |
1867 |
< |
* <pre> |
1868 |
< |
* while (!blocker.isReleasable()) |
1749 |
< |
* if (blocker.block()) |
1750 |
< |
* return; |
1751 |
< |
* </pre> |
1752 |
< |
* If the caller is a ForkJoinTask, then the pool may first |
1753 |
< |
* be expanded to ensure parallelism, and later adjusted. |
1855 |
> |
* is a {@link ForkJoinWorkerThread}, this method possibly |
1856 |
> |
* arranges for a spare thread to be activated if necessary to |
1857 |
> |
* ensure sufficient parallelism while the current thread is blocked. |
1858 |
> |
* |
1859 |
> |
* <p>If the caller is not a {@link ForkJoinTask}, this method is |
1860 |
> |
* behaviorally equivalent to |
1861 |
> |
* <pre> {@code |
1862 |
> |
* while (!blocker.isReleasable()) |
1863 |
> |
* if (blocker.block()) |
1864 |
> |
* return; |
1865 |
> |
* }</pre> |
1866 |
> |
* |
1867 |
> |
* If the caller is a {@code ForkJoinTask}, then the pool may |
1868 |
> |
* first be expanded to ensure parallelism, and later adjusted. |
1869 |
|
* |
1870 |
|
* @param blocker the blocker |
1871 |
< |
* @param maintainParallelism if true and supported by this pool, |
1757 |
< |
* attempt to maintain the pool's nominal parallelism; otherwise |
1758 |
< |
* activate a thread only if necessary to avoid complete |
1759 |
< |
* starvation. |
1760 |
< |
* @throws InterruptedException if blocker.block did so. |
1871 |
> |
* @throws InterruptedException if blocker.block did so |
1872 |
|
*/ |
1873 |
< |
public static void managedBlock(ManagedBlocker blocker, |
1763 |
< |
boolean maintainParallelism) |
1873 |
> |
public static void managedBlock(ManagedBlocker blocker) |
1874 |
|
throws InterruptedException { |
1875 |
|
Thread t = Thread.currentThread(); |
1876 |
< |
ForkJoinPool pool = (t instanceof ForkJoinWorkerThread? |
1877 |
< |
((ForkJoinWorkerThread)t).pool : null); |
1878 |
< |
if (!blocker.isReleasable()) { |
1879 |
< |
try { |
1770 |
< |
if (pool == null || |
1771 |
< |
!pool.preBlock(blocker, maintainParallelism)) |
1772 |
< |
awaitBlocker(blocker); |
1773 |
< |
} finally { |
1774 |
< |
if (pool != null) |
1775 |
< |
pool.updateRunningCount(1); |
1776 |
< |
} |
1876 |
> |
if (t instanceof ForkJoinWorkerThread) |
1877 |
> |
((ForkJoinWorkerThread) t).pool.awaitBlocker(blocker); |
1878 |
> |
else { |
1879 |
> |
do {} while (!blocker.isReleasable() && !blocker.block()); |
1880 |
|
} |
1881 |
|
} |
1882 |
|
|
1883 |
< |
private static void awaitBlocker(ManagedBlocker blocker) |
1884 |
< |
throws InterruptedException { |
1885 |
< |
do;while (!blocker.isReleasable() && !blocker.block()); |
1783 |
< |
} |
1784 |
< |
|
1785 |
< |
// AbstractExecutorService overrides |
1883 |
> |
// AbstractExecutorService overrides. These rely on undocumented |
1884 |
> |
// fact that ForkJoinTask.adapt returns ForkJoinTasks that also |
1885 |
> |
// implement RunnableFuture. |
1886 |
|
|
1887 |
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
1888 |
< |
return new AdaptedRunnable(runnable, value); |
1888 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(runnable, value); |
1889 |
|
} |
1890 |
|
|
1891 |
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
1892 |
< |
return new AdaptedCallable(callable); |
1892 |
> |
return (RunnableFuture<T>) ForkJoinTask.adapt(callable); |
1893 |
|
} |
1894 |
|
|
1895 |
+ |
// Unsafe mechanics |
1896 |
+ |
|
1897 |
+ |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1898 |
+ |
private static final long workerCountsOffset = |
1899 |
+ |
objectFieldOffset("workerCounts", ForkJoinPool.class); |
1900 |
+ |
private static final long runStateOffset = |
1901 |
+ |
objectFieldOffset("runState", ForkJoinPool.class); |
1902 |
+ |
private static final long eventCountOffset = |
1903 |
+ |
objectFieldOffset("eventCount", ForkJoinPool.class); |
1904 |
+ |
private static final long eventWaitersOffset = |
1905 |
+ |
objectFieldOffset("eventWaiters",ForkJoinPool.class); |
1906 |
+ |
private static final long stealCountOffset = |
1907 |
+ |
objectFieldOffset("stealCount",ForkJoinPool.class); |
1908 |
|
|
1909 |
< |
// Temporary Unsafe mechanics for preliminary release |
1797 |
< |
private static Unsafe getUnsafe() throws Throwable { |
1909 |
> |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1910 |
|
try { |
1911 |
< |
return Unsafe.getUnsafe(); |
1911 |
> |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1912 |
> |
} catch (NoSuchFieldException e) { |
1913 |
> |
// Convert Exception to corresponding Error |
1914 |
> |
NoSuchFieldError error = new NoSuchFieldError(field); |
1915 |
> |
error.initCause(e); |
1916 |
> |
throw error; |
1917 |
> |
} |
1918 |
> |
} |
1919 |
> |
|
1920 |
> |
/** |
1921 |
> |
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
1922 |
> |
* Replace with a simple call to Unsafe.getUnsafe when integrating |
1923 |
> |
* into a jdk. |
1924 |
> |
* |
1925 |
> |
* @return a sun.misc.Unsafe |
1926 |
> |
*/ |
1927 |
> |
private static sun.misc.Unsafe getUnsafe() { |
1928 |
> |
try { |
1929 |
> |
return sun.misc.Unsafe.getUnsafe(); |
1930 |
|
} catch (SecurityException se) { |
1931 |
|
try { |
1932 |
|
return java.security.AccessController.doPrivileged |
1933 |
< |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
1934 |
< |
public Unsafe run() throws Exception { |
1935 |
< |
return getUnsafePrivileged(); |
1933 |
> |
(new java.security |
1934 |
> |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
1935 |
> |
public sun.misc.Unsafe run() throws Exception { |
1936 |
> |
java.lang.reflect.Field f = sun.misc |
1937 |
> |
.Unsafe.class.getDeclaredField("theUnsafe"); |
1938 |
> |
f.setAccessible(true); |
1939 |
> |
return (sun.misc.Unsafe) f.get(null); |
1940 |
|
}}); |
1941 |
|
} catch (java.security.PrivilegedActionException e) { |
1942 |
< |
throw e.getCause(); |
1942 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
1943 |
> |
e.getCause()); |
1944 |
|
} |
1945 |
|
} |
1946 |
|
} |
1812 |
– |
|
1813 |
– |
private static Unsafe getUnsafePrivileged() |
1814 |
– |
throws NoSuchFieldException, IllegalAccessException { |
1815 |
– |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1816 |
– |
f.setAccessible(true); |
1817 |
– |
return (Unsafe) f.get(null); |
1818 |
– |
} |
1819 |
– |
|
1820 |
– |
private static long fieldOffset(String fieldName) |
1821 |
– |
throws NoSuchFieldException { |
1822 |
– |
return _unsafe.objectFieldOffset |
1823 |
– |
(ForkJoinPool.class.getDeclaredField(fieldName)); |
1824 |
– |
} |
1825 |
– |
|
1826 |
– |
static final Unsafe _unsafe; |
1827 |
– |
static final long eventCountOffset; |
1828 |
– |
static final long workerCountsOffset; |
1829 |
– |
static final long runControlOffset; |
1830 |
– |
static final long syncStackOffset; |
1831 |
– |
static final long spareStackOffset; |
1832 |
– |
|
1833 |
– |
static { |
1834 |
– |
try { |
1835 |
– |
_unsafe = getUnsafe(); |
1836 |
– |
eventCountOffset = fieldOffset("eventCount"); |
1837 |
– |
workerCountsOffset = fieldOffset("workerCounts"); |
1838 |
– |
runControlOffset = fieldOffset("runControl"); |
1839 |
– |
syncStackOffset = fieldOffset("syncStack"); |
1840 |
– |
spareStackOffset = fieldOffset("spareStack"); |
1841 |
– |
} catch (Throwable e) { |
1842 |
– |
throw new RuntimeException("Could not initialize intrinsics", e); |
1843 |
– |
} |
1844 |
– |
} |
1845 |
– |
|
1846 |
– |
private boolean casEventCount(long cmp, long val) { |
1847 |
– |
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1848 |
– |
} |
1849 |
– |
private boolean casWorkerCounts(int cmp, int val) { |
1850 |
– |
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1851 |
– |
} |
1852 |
– |
private boolean casRunControl(int cmp, int val) { |
1853 |
– |
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
1854 |
– |
} |
1855 |
– |
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1856 |
– |
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1857 |
– |
} |
1858 |
– |
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1859 |
– |
return _unsafe.compareAndSwapObject(this, syncStackOffset, cmp, val); |
1860 |
– |
} |
1947 |
|
} |