… | |
… | |
53 | |
53 | |
54 | For example the deliantra game server uses a variant of this technique |
54 | For example the deliantra game server uses a variant of this technique |
55 | to interrupt background processes regularly to send map updates to game |
55 | to interrupt background processes regularly to send map updates to game |
56 | clients. |
56 | clients. |
57 | |
57 | |
|
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58 | Or L<EV::Loop::Async> uses an interrupt object to wake up perl when new |
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59 | events have arrived. |
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60 | |
58 | L<IO::AIO> and L<BDB> could also use this to speed up result reporting. |
61 | L<IO::AIO> and L<BDB> could also use this to speed up result reporting. |
59 | |
62 | |
60 | =item Speedy event loop invocation |
63 | =item Speedy event loop invocation |
61 | |
64 | |
62 | One could use this module e.g. in L<Coro> to interrupt a running coro-thread |
65 | One could use this module e.g. in L<Coro> to interrupt a running coro-thread |
… | |
… | |
88 | I<running> interpreter, there is optional support for signalling a pipe |
91 | I<running> interpreter, there is optional support for signalling a pipe |
89 | - that means you can also wait for the pipe to become readable (e.g. via |
92 | - that means you can also wait for the pipe to become readable (e.g. via |
90 | L<EV> or L<AnyEvent>). This, of course, incurs the overhead of a C<read> |
93 | L<EV> or L<AnyEvent>). This, of course, incurs the overhead of a C<read> |
91 | and C<write> syscall. |
94 | and C<write> syscall. |
92 | |
95 | |
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96 | =head1 THE Async::Interrupt CLASS |
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97 | |
93 | =over 4 |
98 | =over 4 |
94 | |
99 | |
95 | =cut |
100 | =cut |
96 | |
101 | |
97 | package Async::Interrupt; |
102 | package Async::Interrupt; |
98 | |
103 | |
99 | no warnings; |
104 | use common::sense; |
100 | |
105 | |
101 | BEGIN { |
106 | BEGIN { |
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107 | # the next line forces initialisation of internal |
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108 | # signal handling # variables |
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109 | $SIG{KILL} = sub { }; |
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110 | |
102 | $VERSION = '0.04'; |
111 | our $VERSION = '0.6'; |
103 | |
112 | |
104 | require XSLoader; |
113 | require XSLoader; |
105 | XSLoader::load Async::Interrupt::, $VERSION; |
114 | XSLoader::load ("Async::Interrupt", $VERSION); |
106 | } |
115 | } |
107 | |
116 | |
108 | our $DIED = sub { warn "$@" }; |
117 | our $DIED = sub { warn "$@" }; |
109 | |
118 | |
110 | =item $async = new Async::Interrupt key => value... |
119 | =item $async = new Async::Interrupt key => value... |
… | |
… | |
153 | might use (the exception is C<errno>, which is saved and restored by |
162 | might use (the exception is C<errno>, which is saved and restored by |
154 | Async::Interrupt). The callback itself runs as part of the perl context, |
163 | Async::Interrupt). The callback itself runs as part of the perl context, |
155 | so you can call any perl functions and modify any perl data structures (in |
164 | so you can call any perl functions and modify any perl data structures (in |
156 | which case the requirements set out for C<cb> apply as well). |
165 | which case the requirements set out for C<cb> apply as well). |
157 | |
166 | |
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167 | =item var => $scalar_ref |
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168 | |
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169 | When specified, then the given argument must be a reference to a |
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170 | scalar. The scalar will be set to C<0> initially. Signalling the interrupt |
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171 | object will set it to the passed value, handling the interrupt will reset |
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172 | it to C<0> again. |
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173 | |
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174 | Note that the only thing you are legally allowed to do is to is to check |
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175 | the variable in a boolean or integer context (e.g. comparing it with a |
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176 | string, or printing it, will I<destroy> it and might cause your program to |
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177 | crash or worse). |
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178 | |
158 | =item signal => $signame_or_value |
179 | =item signal => $signame_or_value |
159 | |
180 | |
160 | When this parameter is specified, then the Async::Interrupt will hook the |
181 | When this parameter is specified, then the Async::Interrupt will hook the |
161 | given signal, that is, it will effectively call C<< ->signal (0) >> each time |
182 | given signal, that is, it will effectively call C<< ->signal (0) >> each time |
162 | the given signal is caught by the process. |
183 | the given signal is caught by the process. |
… | |
… | |
171 | be written to it, and before the callback is being invoked, it will be |
192 | be written to it, and before the callback is being invoked, it will be |
172 | read again. Due to races, it is unlikely but possible that multiple octets |
193 | read again. Due to races, it is unlikely but possible that multiple octets |
173 | are written. It is required that the file handles are both in nonblocking |
194 | are written. It is required that the file handles are both in nonblocking |
174 | mode. |
195 | mode. |
175 | |
196 | |
176 | You can get a portable pipe and set non-blocking mode portably by using |
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177 | e.g. L<AnyEvent::Util> from the L<AnyEvent> distribution. |
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178 | |
|
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179 | It is also possible to pass in a linux eventfd as both read and write |
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180 | handle (which is faster than a pipe). |
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181 | |
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182 | The object will keep a reference to the file handles. |
197 | The object will keep a reference to the file handles. |
183 | |
198 | |
184 | This can be used to ensure that async notifications will interrupt event |
199 | This can be used to ensure that async notifications will interrupt event |
185 | frameworks as well. |
200 | frameworks as well. |
186 | |
201 | |
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202 | Note that C<Async::Interrupt> will create a suitable signal fd |
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203 | automatically when your program requests one, so you don't have to specify |
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204 | this argument when all you want is an extra file descriptor to watch. |
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205 | |
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206 | If you want to share a single event pipe between multiple Async::Interrupt |
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207 | objects, you can use the C<Async::Interrupt::EventPipe> class to manage |
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208 | those. |
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209 | |
187 | =back |
210 | =back |
188 | |
211 | |
189 | =cut |
212 | =cut |
190 | |
213 | |
191 | sub new { |
214 | sub new { |
192 | my ($class, %arg) = @_; |
215 | my ($class, %arg) = @_; |
193 | |
216 | |
194 | bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}), $class |
217 | bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class |
195 | } |
218 | } |
196 | |
219 | |
197 | =item ($signal_func, $signal_arg) = $async->signal_func |
220 | =item ($signal_func, $signal_arg) = $async->signal_func |
198 | |
221 | |
199 | Returns the address of a function to call asynchronously. The function has |
222 | Returns the address of a function to call asynchronously. The function |
200 | the following prototype and needs to be passed the specified C<$c_arg>, |
223 | has the following prototype and needs to be passed the specified |
201 | which is a C<void *> cast to C<IV>: |
224 | C<$signal_arg>, which is a C<void *> cast to C<IV>: |
202 | |
225 | |
203 | void (*signal_func) (void *signal_arg, int value) |
226 | void (*signal_func) (void *signal_arg, int value) |
204 | |
227 | |
205 | An example call would look like: |
228 | An example call would look like: |
206 | |
229 | |
207 | signal_func (signal_arg, 0); |
230 | signal_func (signal_arg, 0); |
208 | |
231 | |
209 | The function is safe to call from within signal and thread contexts, at |
232 | The function is safe to call from within signal and thread contexts, at |
210 | any time. The specified C<value> is passed to both C and Perl callback. |
233 | any time. The specified C<value> is passed to both C and Perl callback. |
211 | |
234 | |
212 | C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is |
235 | C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0> |
213 | portable). |
236 | (1..127 is portable). |
214 | |
237 | |
215 | If the function is called while the Async::Interrupt object is already |
238 | If the function is called while the Async::Interrupt object is already |
216 | signaled but before the callbacks are being executed, then the stored |
239 | signaled but before the callbacks are being executed, then the stored |
217 | C<value> is either the old or the new one. Due to the asynchronous |
240 | C<value> is either the old or the new one. Due to the asynchronous |
218 | nature of the code, the C<value> can even be passed to two consecutive |
241 | nature of the code, the C<value> can even be passed to two consecutive |
219 | invocations of the callback. |
242 | invocations of the callback. |
220 | |
243 | |
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244 | =item $address = $async->c_var |
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245 | |
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246 | Returns the address (cast to IV) of an C<IV> variable. The variable is set |
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247 | to C<0> initially and gets set to the passed value whenever the object |
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248 | gets signalled, and reset to C<0> once the interrupt has been handled. |
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249 | |
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250 | Note that it is often beneficial to just call C<PERL_ASYNC_CHECK ()> to |
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251 | handle any interrupts. |
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252 | |
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253 | Example: call some XS function to store the address, then show C code |
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254 | waiting for it. |
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255 | |
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256 | my_xs_func $async->c_var; |
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257 | |
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258 | static IV *valuep; |
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259 | |
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260 | void |
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261 | my_xs_func (void *addr) |
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262 | CODE: |
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263 | valuep = (IV *)addr; |
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264 | |
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265 | // code in a loop, waiting |
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266 | while (!*valuep) |
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267 | ; // do something |
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268 | |
221 | =item $async->signal ($value=0) |
269 | =item $async->signal ($value=1) |
222 | |
270 | |
223 | This signals the given async object from Perl code. Semi-obviously, this |
271 | This signals the given async object from Perl code. Semi-obviously, this |
224 | will instantly trigger the callback invocation. |
272 | will instantly trigger the callback invocation (it does not, as the name |
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273 | might imply, do anything with POSIX signals). |
225 | |
274 | |
226 | C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is |
275 | C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0> |
227 | portable). |
276 | (1..127 is portable). |
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277 | |
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278 | =item $async->signal_hysteresis ($enable) |
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279 | |
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280 | Enables or disables signal hysteresis (default: disabled). If a POSIX |
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281 | signal is used as a signal source for the interrupt object, then enabling |
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282 | signal hysteresis causes Async::Interrupt to reset the signal action to |
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283 | C<SIG_IGN> in the signal handler and restore it just before handling the |
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284 | interruption. |
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285 | |
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286 | When you expect a lot of signals (e.g. when using SIGIO), then enabling |
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287 | signal hysteresis can reduce the number of handler invocations |
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288 | considerably, at the cost of two extra syscalls. |
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289 | |
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290 | Note that setting the signal to C<SIG_IGN> can have unintended side |
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291 | effects when you fork and exec other programs, as often they do nto expect |
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292 | signals to be ignored by default. |
228 | |
293 | |
229 | =item $async->block |
294 | =item $async->block |
230 | |
295 | |
231 | =item $async->unblock |
296 | =item $async->unblock |
232 | |
297 | |
… | |
… | |
247 | This call C<< $async->block >> and installs a handler that is called when |
312 | This call C<< $async->block >> and installs a handler that is called when |
248 | the current scope is exited (via an exception, by canceling the Coro |
313 | the current scope is exited (via an exception, by canceling the Coro |
249 | thread, by calling last/goto etc.). |
314 | thread, by calling last/goto etc.). |
250 | |
315 | |
251 | This is the recommended (and fastest) way to implement critical sections. |
316 | This is the recommended (and fastest) way to implement critical sections. |
|
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317 | |
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318 | =item ($block_func, $block_arg) = $async->scope_block_func |
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319 | |
|
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320 | Returns the address of a function that implements the C<scope_block> |
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321 | functionality. |
|
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322 | |
|
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323 | It has the following prototype and needs to be passed the specified |
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324 | C<$block_arg>, which is a C<void *> cast to C<IV>: |
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325 | |
|
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326 | void (*block_func) (void *block_arg) |
|
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327 | |
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328 | An example call would look like: |
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329 | |
|
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330 | block_func (block_arg); |
|
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331 | |
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332 | The function is safe to call only from within the toplevel of a perl XS |
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333 | function and will call C<LEAVE> and C<ENTER> (in this order!). |
252 | |
334 | |
253 | =item $async->pipe_enable |
335 | =item $async->pipe_enable |
254 | |
336 | |
255 | =item $async->pipe_disable |
337 | =item $async->pipe_disable |
256 | |
338 | |
… | |
… | |
258 | enabled). Writing to a pipe is relatively expensive, so it can be disabled |
340 | enabled). Writing to a pipe is relatively expensive, so it can be disabled |
259 | when you know you are not waiting for it (for example, with L<EV> you |
341 | when you know you are not waiting for it (for example, with L<EV> you |
260 | could disable the pipe in a check watcher, and enable it in a prepare |
342 | could disable the pipe in a check watcher, and enable it in a prepare |
261 | watcher). |
343 | watcher). |
262 | |
344 | |
263 | Note that when C<fd_disable> is in effect, no attempt to read from the |
345 | Note that currently, while C<pipe_disable> is in effect, no attempt to |
264 | pipe will be done. |
346 | read from the pipe will be done when handling events. This might change as |
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347 | soon as I realize why this is a mistake. |
|
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348 | |
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349 | =item $fileno = $async->pipe_fileno |
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350 | |
|
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351 | Returns the reading side of the signalling pipe. If no signalling pipe is |
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352 | currently attached to the object, it will dynamically create one. |
|
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353 | |
|
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354 | Note that the only valid oepration on this file descriptor is to wait |
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355 | until it is readable. The fd might belong currently to a pipe, a tcp |
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356 | socket, or an eventfd, depending on the platform, and is guaranteed to be |
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357 | C<select>able. |
|
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358 | |
|
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359 | =item $async->pipe_autodrain ($enable) |
|
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360 | |
|
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361 | Enables (C<1>) or disables (C<0>) automatic draining of the pipe (default: |
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362 | enabled). When automatic draining is enabled, then Async::Interrupt will |
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363 | automatically clear the pipe. Otherwise the user is responsible for this |
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364 | draining. |
|
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365 | |
|
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366 | This is useful when you want to share one pipe among many Async::Interrupt |
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367 | objects. |
|
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368 | |
|
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369 | =item $async->post_fork |
|
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370 | |
|
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371 | The object will not normally be usable after a fork (as the pipe fd is |
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372 | shared between processes). Calling this method after a fork in the child |
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373 | ensures that the object will work as expected again. It only needs to be |
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374 | called when the async object is used in the child. |
|
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375 | |
|
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376 | This only works when the pipe was created by Async::Interrupt. |
|
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377 | |
|
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378 | Async::Interrupt ensures that the reading file descriptor does not change |
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379 | it's value. |
|
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380 | |
|
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381 | =back |
|
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382 | |
|
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383 | =head1 THE Async::Interrupt::EventPipe CLASS |
|
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384 | |
|
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385 | Pipes are the predominent utility to make asynchronous signals |
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386 | synchronous. However, pipes are hard to come by: they don't exist on the |
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387 | broken windows platform, and on GNU/Linux systems, you might want to use |
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388 | an C<eventfd> instead. |
|
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389 | |
|
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390 | This class creates selectable event pipes in a portable fashion: on |
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391 | windows, it will try to create a tcp socket pair, on GNU/Linux, it will |
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392 | try to create an eventfd and everywhere else it will try to use a normal |
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393 | pipe. |
|
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394 | |
|
|
395 | =over 4 |
|
|
396 | |
|
|
397 | =item $epipe = new Async::Interrupt::EventPipe |
|
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398 | |
|
|
399 | This creates and returns an eventpipe object. This object is simply a |
|
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400 | blessed array reference: |
|
|
401 | |
|
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402 | =item ($r_fd, $w_fd) = $epipe->filenos |
|
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403 | |
|
|
404 | Returns the read-side file descriptor and the write-side file descriptor. |
|
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405 | |
|
|
406 | Example: pass an eventpipe object as pipe to the Async::Interrupt |
|
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407 | constructor, and create an AnyEvent watcher for the read side. |
|
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408 | |
|
|
409 | my $epipe = new Async::Interrupt::EventPipe; |
|
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410 | my $asy = new Async::Interrupt pipe => [$epipe->filenos]; |
|
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411 | my $iow = AnyEvent->io (fh => $epipe->fileno, poll => 'r', cb => sub { }); |
|
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412 | |
|
|
413 | =item $r_fd = $epipe->fileno |
|
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414 | |
|
|
415 | Return only the reading/listening side. |
|
|
416 | |
|
|
417 | =item $epipe->signal |
|
|
418 | |
|
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419 | Write something to the pipe, in a portable fashion. |
|
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420 | |
|
|
421 | =item $epipe->drain |
|
|
422 | |
|
|
423 | Drain (empty) the pipe. |
|
|
424 | |
|
|
425 | =item $epipe->renew |
|
|
426 | |
|
|
427 | Recreates the pipe (useful after a fork). The reading side will not change |
|
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428 | it's file descriptor number, but the writing side might. |
|
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429 | |
|
|
430 | =back |
265 | |
431 | |
266 | =cut |
432 | =cut |
267 | |
433 | |
268 | 1; |
434 | 1; |
269 | |
|
|
270 | =back |
|
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271 | |
435 | |
272 | =head1 EXAMPLE |
436 | =head1 EXAMPLE |
273 | |
437 | |
274 | There really should be a complete C/XS example. Bug me about it. Better |
438 | There really should be a complete C/XS example. Bug me about it. Better |
275 | yet, create one. |
439 | yet, create one. |
… | |
… | |
283 | then intercepts the interpreter handling it. This makes normal signal |
447 | then intercepts the interpreter handling it. This makes normal signal |
284 | handling slower (probably unmeasurably, though), but has the advantage |
448 | handling slower (probably unmeasurably, though), but has the advantage |
285 | of not requiring a special runops function, nor slowing down normal perl |
449 | of not requiring a special runops function, nor slowing down normal perl |
286 | execution a bit. |
450 | execution a bit. |
287 | |
451 | |
288 | It assumes that C<sig_atomic_t> and C<int> are both async-safe to modify |
452 | It assumes that C<sig_atomic_t>, C<int> and C<IV> are all async-safe to |
289 | (C<sig_atomic_> is used by this module, and perl itself uses C<int>, so we |
453 | modify. |
290 | can assume that this is quite portable, at least w.r.t. signals). |
|
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291 | |
454 | |
292 | =head1 AUTHOR |
455 | =head1 AUTHOR |
293 | |
456 | |
294 | Marc Lehmann <schmorp@schmorp.de> |
457 | Marc Lehmann <schmorp@schmorp.de> |
295 | http://home.schmorp.de/ |
458 | http://home.schmorp.de/ |