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18 | |
18 | |
19 | cede; |
19 | cede; |
20 | |
20 | |
21 | =head1 DESCRIPTION |
21 | =head1 DESCRIPTION |
22 | |
22 | |
23 | This module collection manages coroutines. Coroutines are similar to |
23 | This module collection manages coroutines. Coroutines are similar |
24 | threads but don't run in parallel. |
24 | to threads but don't run in parallel at the same time even on SMP |
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25 | machines. The specific flavor of coroutine use din this module also |
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26 | guarentees you that it will not switch between coroutines unless |
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27 | necessary, at easily-identified points in your program, so locking and |
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28 | parallel access are rarely an issue, making coroutine programming much |
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29 | safer than threads programming. |
25 | |
30 | |
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31 | (Perl, however, does not natively support real threads but instead does a |
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32 | very slow and memory-intensive emulation of processes using threads. This |
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33 | is a performance win on Windows machines, and a loss everywhere else). |
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34 | |
26 | In this module, coroutines are defined as "callchain + lexical variables |
35 | In this module, coroutines are defined as "callchain + lexical variables + |
27 | + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own |
36 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
28 | callchain, it's own set of lexicals and it's own set of perl's most |
37 | its own set of lexicals and its own set of perls most important global |
29 | important global variables. |
38 | variables. |
30 | |
39 | |
31 | =cut |
40 | =cut |
32 | |
41 | |
33 | package Coro; |
42 | package Coro; |
34 | |
43 | |
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41 | |
50 | |
42 | our $idle; # idle handler |
51 | our $idle; # idle handler |
43 | our $main; # main coroutine |
52 | our $main; # main coroutine |
44 | our $current; # current coroutine |
53 | our $current; # current coroutine |
45 | |
54 | |
46 | our $VERSION = '3.01'; |
55 | our $VERSION = '3.3'; |
47 | |
56 | |
48 | our @EXPORT = qw(async cede schedule terminate current unblock_sub); |
57 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
49 | our %EXPORT_TAGS = ( |
58 | our %EXPORT_TAGS = ( |
50 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
59 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
51 | ); |
60 | ); |
52 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
61 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
53 | |
62 | |
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132 | $idle = sub { |
141 | $idle = sub { |
133 | require Carp; |
142 | require Carp; |
134 | Carp::croak ("FATAL: deadlock detected"); |
143 | Carp::croak ("FATAL: deadlock detected"); |
135 | }; |
144 | }; |
136 | |
145 | |
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146 | sub _cancel { |
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147 | my ($self) = @_; |
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148 | |
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149 | # free coroutine data and mark as destructed |
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150 | $self->_destroy |
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151 | or return; |
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152 | |
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153 | # call all destruction callbacks |
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154 | $_->(@{$self->{status}}) |
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155 | for @{(delete $self->{destroy_cb}) || []}; |
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156 | } |
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157 | |
137 | # this coroutine is necessary because a coroutine |
158 | # this coroutine is necessary because a coroutine |
138 | # cannot destroy itself. |
159 | # cannot destroy itself. |
139 | my @destroy; |
160 | my @destroy; |
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161 | my $manager; |
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162 | |
140 | my $manager; $manager = new Coro sub { |
163 | $manager = new Coro sub { |
141 | while () { |
164 | while () { |
142 | # by overwriting the state object with the manager we destroy it |
165 | (shift @destroy)->_cancel |
143 | # while still being able to schedule this coroutine (in case it has |
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144 | # been readied multiple times. this is harmless since the manager |
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145 | # can be called as many times as neccessary and will always |
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146 | # remove itself from the runqueue |
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147 | while (@destroy) { |
166 | while @destroy; |
148 | my $coro = pop @destroy; |
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149 | $coro->{status} ||= []; |
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150 | $_->ready for @{delete $coro->{join} || []}; |
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151 | |
167 | |
152 | # the next line destroys the coro state, but keeps the |
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153 | # coroutine itself intact (we basically make it a zombie |
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154 | # coroutine that always runs the manager thread, so it's possible |
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155 | # to transfer() to this coroutine). |
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156 | $coro->_clone_state_from ($manager); |
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157 | } |
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158 | &schedule; |
168 | &schedule; |
159 | } |
169 | } |
160 | }; |
170 | }; |
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171 | |
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172 | $manager->prio (PRIO_MAX); |
161 | |
173 | |
162 | # static methods. not really. |
174 | # static methods. not really. |
163 | |
175 | |
164 | =back |
176 | =back |
165 | |
177 | |
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186 | } 1,2,3,4; |
198 | } 1,2,3,4; |
187 | |
199 | |
188 | =cut |
200 | =cut |
189 | |
201 | |
190 | sub async(&@) { |
202 | sub async(&@) { |
191 | my $pid = new Coro @_; |
203 | my $coro = new Coro @_; |
192 | $pid->ready; |
204 | $coro->ready; |
193 | $pid |
205 | $coro |
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206 | } |
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207 | |
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208 | =item async_pool { ... } [@args...] |
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209 | |
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210 | Similar to C<async>, but uses a coroutine pool, so you should not call |
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211 | terminate or join (although you are allowed to), and you get a coroutine |
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212 | that might have executed other code already (which can be good or bad :). |
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213 | |
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214 | Also, the block is executed in an C<eval> context and a warning will be |
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215 | issued in case of an exception instead of terminating the program, as |
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216 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
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217 | will not work in the expected way, unless you call terminate or cancel, |
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218 | which somehow defeats the purpose of pooling. |
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219 | |
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220 | The priority will be reset to C<0> after each job, otherwise the coroutine |
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221 | will be re-used "as-is". |
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222 | |
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223 | The pool size is limited to 8 idle coroutines (this can be adjusted by |
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224 | changing $Coro::POOL_SIZE), and there can be as many non-idle coros as |
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225 | required. |
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226 | |
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227 | If you are concerned about pooled coroutines growing a lot because a |
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228 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool { |
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229 | terminate }> once per second or so to slowly replenish the pool. |
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230 | |
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231 | =cut |
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232 | |
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233 | our $POOL_SIZE = 8; |
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234 | our @pool; |
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235 | |
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236 | sub pool_handler { |
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237 | while () { |
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238 | eval { |
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239 | my ($cb, @arg) = @{ delete $current->{_invoke} or return }; |
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240 | $cb->(@arg); |
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241 | }; |
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242 | warn $@ if $@; |
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243 | |
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244 | last if @pool >= $POOL_SIZE; |
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245 | push @pool, $current; |
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246 | |
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247 | $current->prio (0); |
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248 | schedule; |
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249 | } |
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250 | } |
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251 | |
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252 | sub async_pool(&@) { |
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253 | # this is also inlined into the unlock_scheduler |
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254 | my $coro = (pop @pool or new Coro \&pool_handler); |
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255 | |
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256 | $coro->{_invoke} = [@_]; |
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257 | $coro->ready; |
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258 | |
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259 | $coro |
194 | } |
260 | } |
195 | |
261 | |
196 | =item schedule |
262 | =item schedule |
197 | |
263 | |
198 | Calls the scheduler. Please note that the current coroutine will not be put |
264 | Calls the scheduler. Please note that the current coroutine will not be put |
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223 | |
289 | |
224 | "Cede" to other coroutines. This function puts the current coroutine into the |
290 | "Cede" to other coroutines. This function puts the current coroutine into the |
225 | ready queue and calls C<schedule>, which has the effect of giving up the |
291 | ready queue and calls C<schedule>, which has the effect of giving up the |
226 | current "timeslice" to other coroutines of the same or higher priority. |
292 | current "timeslice" to other coroutines of the same or higher priority. |
227 | |
293 | |
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294 | Returns true if at least one coroutine switch has happened. |
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295 | |
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296 | =item Coro::cede_notself |
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297 | |
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298 | Works like cede, but is not exported by default and will cede to any |
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299 | coroutine, regardless of priority, once. |
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300 | |
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301 | Returns true if at least one coroutine switch has happened. |
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302 | |
228 | =item terminate [arg...] |
303 | =item terminate [arg...] |
229 | |
304 | |
230 | Terminates the current coroutine with the given status values (see L<cancel>). |
305 | Terminates the current coroutine with the given status values (see L<cancel>). |
231 | |
306 | |
232 | =cut |
307 | =cut |
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277 | Return wether the coroutine is currently the ready queue or not, |
352 | Return wether the coroutine is currently the ready queue or not, |
278 | |
353 | |
279 | =item $coroutine->cancel (arg...) |
354 | =item $coroutine->cancel (arg...) |
280 | |
355 | |
281 | Terminates the given coroutine and makes it return the given arguments as |
356 | Terminates the given coroutine and makes it return the given arguments as |
282 | status (default: the empty list). |
357 | status (default: the empty list). Never returns if the coroutine is the |
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358 | current coroutine. |
283 | |
359 | |
284 | =cut |
360 | =cut |
285 | |
361 | |
286 | sub cancel { |
362 | sub cancel { |
287 | my $self = shift; |
363 | my $self = shift; |
288 | $self->{status} = [@_]; |
364 | $self->{status} = [@_]; |
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365 | |
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366 | if ($current == $self) { |
289 | push @destroy, $self; |
367 | push @destroy, $self; |
290 | $manager->ready; |
368 | $manager->ready; |
291 | &schedule if $current == $self; |
369 | &schedule while 1; |
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370 | } else { |
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371 | $self->_cancel; |
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372 | } |
292 | } |
373 | } |
293 | |
374 | |
294 | =item $coroutine->join |
375 | =item $coroutine->join |
295 | |
376 | |
296 | Wait until the coroutine terminates and return any values given to the |
377 | Wait until the coroutine terminates and return any values given to the |
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299 | |
380 | |
300 | =cut |
381 | =cut |
301 | |
382 | |
302 | sub join { |
383 | sub join { |
303 | my $self = shift; |
384 | my $self = shift; |
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385 | |
304 | unless ($self->{status}) { |
386 | unless ($self->{status}) { |
305 | push @{$self->{join}}, $current; |
387 | my $current = $current; |
306 | &schedule; |
388 | |
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389 | push @{$self->{destroy_cb}}, sub { |
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390 | $current->ready; |
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391 | undef $current; |
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392 | }; |
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393 | |
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394 | &schedule while $current; |
307 | } |
395 | } |
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396 | |
308 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
397 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
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398 | } |
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399 | |
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400 | =item $coroutine->on_destroy (\&cb) |
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401 | |
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402 | Registers a callback that is called when this coroutine gets destroyed, |
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403 | but before it is joined. The callback gets passed the terminate arguments, |
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404 | if any. |
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405 | |
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406 | =cut |
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407 | |
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408 | sub on_destroy { |
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409 | my ($self, $cb) = @_; |
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410 | |
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411 | push @{ $self->{destroy_cb} }, $cb; |
309 | } |
412 | } |
310 | |
413 | |
311 | =item $oldprio = $coroutine->prio ($newprio) |
414 | =item $oldprio = $coroutine->prio ($newprio) |
312 | |
415 | |
313 | Sets (or gets, if the argument is missing) the priority of the |
416 | Sets (or gets, if the argument is missing) the priority of the |
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360 | i.e. that can be swicthed to. The value C<0> means that the only runnable |
463 | i.e. that can be swicthed to. The value C<0> means that the only runnable |
361 | coroutine is the currently running one, so C<cede> would have no effect, |
464 | coroutine is the currently running one, so C<cede> would have no effect, |
362 | and C<schedule> would cause a deadlock unless there is an idle handler |
465 | and C<schedule> would cause a deadlock unless there is an idle handler |
363 | that wakes up some coroutines. |
466 | that wakes up some coroutines. |
364 | |
467 | |
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468 | =item my $guard = Coro::guard { ... } |
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469 | |
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470 | This creates and returns a guard object. Nothing happens until the objetc |
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471 | gets destroyed, in which case the codeblock given as argument will be |
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472 | executed. This is useful to free locks or other resources in case of a |
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473 | runtime error or when the coroutine gets canceled, as in both cases the |
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474 | guard block will be executed. The guard object supports only one method, |
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475 | C<< ->cancel >>, which will keep the codeblock from being executed. |
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476 | |
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477 | Example: set some flag and clear it again when the coroutine gets canceled |
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478 | or the function returns: |
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479 | |
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480 | sub do_something { |
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481 | my $guard = Coro::guard { $busy = 0 }; |
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482 | $busy = 1; |
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483 | |
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484 | # do something that requires $busy to be true |
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485 | } |
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486 | |
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487 | =cut |
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488 | |
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489 | sub guard(&) { |
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490 | bless \(my $cb = $_[0]), "Coro::guard" |
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491 | } |
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492 | |
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493 | sub Coro::guard::cancel { |
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494 | ${$_[0]} = sub { }; |
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495 | } |
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496 | |
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497 | sub Coro::guard::DESTROY { |
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498 | ${$_[0]}->(); |
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499 | } |
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500 | |
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501 | |
365 | =item unblock_sub { ... } |
502 | =item unblock_sub { ... } |
366 | |
503 | |
367 | This utility function takes a BLOCK or code reference and "unblocks" it, |
504 | This utility function takes a BLOCK or code reference and "unblocks" it, |
368 | returning the new coderef. This means that the new coderef will return |
505 | returning the new coderef. This means that the new coderef will return |
369 | immediately without blocking, returning nothing, while the original code |
506 | immediately without blocking, returning nothing, while the original code |
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382 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
519 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
383 | creating event callbacks that want to block. |
520 | creating event callbacks that want to block. |
384 | |
521 | |
385 | =cut |
522 | =cut |
386 | |
523 | |
387 | our @unblock_pool; |
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388 | our @unblock_queue; |
524 | our @unblock_queue; |
389 | our $UNBLOCK_POOL_SIZE = 2; |
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390 | |
525 | |
391 | sub unblock_handler_ { |
526 | # we create a special coro because we want to cede, |
392 | while () { |
527 | # to reduce pressure on the coro pool (because most callbacks |
393 | my ($cb, @arg) = @{ delete $Coro::current->{arg} }; |
528 | # return immediately and can be reused) and because we cannot cede |
394 | $cb->(@arg); |
529 | # inside an event callback. |
395 | |
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396 | last if @unblock_pool >= $UNBLOCK_POOL_SIZE; |
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397 | push @unblock_pool, $Coro::current; |
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398 | schedule; |
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399 | } |
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400 | } |
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401 | |
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402 | our $unblock_scheduler = async { |
530 | our $unblock_scheduler = async { |
403 | while () { |
531 | while () { |
404 | while (my $cb = pop @unblock_queue) { |
532 | while (my $cb = pop @unblock_queue) { |
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533 | # this is an inlined copy of async_pool |
405 | my $handler = (pop @unblock_pool or new Coro \&unblock_handler_); |
534 | my $coro = (pop @pool or new Coro \&pool_handler); |
406 | $handler->{arg} = $cb; |
535 | |
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536 | $coro->{_invoke} = $cb; |
407 | $handler->ready; |
537 | $coro->ready; |
408 | cede; |
538 | cede; # for short-lived callbacks, this reduces pressure on the coro pool |
409 | } |
539 | } |
410 | |
540 | schedule; # sleep well |
411 | schedule; |
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412 | } |
541 | } |
413 | }; |
542 | }; |
414 | |
543 | |
415 | sub unblock_sub(&) { |
544 | sub unblock_sub(&) { |
416 | my $cb = shift; |
545 | my $cb = shift; |
417 | |
546 | |
418 | sub { |
547 | sub { |
419 | push @unblock_queue, [$cb, @_]; |
548 | unshift @unblock_queue, [$cb, @_]; |
420 | $unblock_scheduler->ready; |
549 | $unblock_scheduler->ready; |
421 | } |
550 | } |
422 | } |
551 | } |
423 | |
552 | |
424 | =back |
553 | =back |