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140 | =head2 Interrupt perl from another thread |
140 | =head2 Interrupt perl from another thread |
141 | |
141 | |
142 | This example interrupts the Perl interpreter from another thread, via the |
142 | This example interrupts the Perl interpreter from another thread, via the |
143 | XS API. This is used by e.g. the L<EV::Loop::Async> module. |
143 | XS API. This is used by e.g. the L<EV::Loop::Async> module. |
144 | |
144 | |
145 | #TODO# |
145 | On the Perl level, a new loop object (which contains the thread) |
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146 | is created, by first calling some XS constructor, querying the |
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147 | C-level callback function and feeding that as the C<c_cb> into the |
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148 | Async::Interrupt constructor: |
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149 | |
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150 | my $self = XS_thread_constructor; |
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151 | my ($c_func, $c_arg) = _c_func $self; # return the c callback |
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152 | my $asy = new Async::Interrupt c_cb => [$c_func, $c_arg]; |
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153 | |
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154 | Then the newly created Interrupt object is queried for the signaling |
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155 | function that the newly created thread should call, and this is in turn |
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156 | told to the thread object: |
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157 | |
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158 | _attach $self, $asy->signal_func; |
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159 | |
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160 | So to repeat: first the XS object is created, then it is queried for the |
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161 | callback that should be called when the Interrupt object gets signalled. |
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162 | |
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163 | Then the interrupt object is queried for the callback fucntion that the |
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164 | thread should call to signal the Interrupt object, and this callback is |
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165 | then attached to the thread. |
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166 | |
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167 | You have to be careful that your new thread is not signalling before the |
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168 | signal function was configured, for example by starting the background |
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169 | thread only within C<_attach>. |
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170 | |
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171 | That concludes the Perl part. |
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172 | |
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173 | The XS part consists of the actual constructor which creates a thread, |
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174 | which is not relevant for this example, and two functions, C<_c_func>, |
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175 | which returns the Perl-side callback, and C<_attach>, which configures |
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176 | the signalling functioon that is safe toc all from another thread. For |
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177 | simplicity, we will use global variables to store the functions, normally |
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178 | you would somehow attach them to C<$self>. |
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179 | |
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180 | The C<c_func> simply returns the address of a static function and arranges |
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181 | for the object pointed to by C<$self> to be passed to it, as an integer: |
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182 | |
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183 | void |
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184 | _c_func (SV *loop) |
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185 | PPCODE: |
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186 | EXTEND (SP, 2); |
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187 | PUSHs (sv_2mortal (newSViv (PTR2IV (c_func)))); |
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188 | PUSHs (sv_2mortal (newSViv (SvRV (loop)))); |
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189 | |
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190 | This would be the callback (since it runs in a normal Perl context, it is |
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191 | permissible to manipulate Perl values): |
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192 | |
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193 | static void |
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194 | c_func (pTHX_ void *loop_, int value) |
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195 | { |
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196 | SV *loop_object = (SV *)loop_; |
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197 | ... |
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198 | } |
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199 | |
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200 | And this attaches the signalling callback: |
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201 | |
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202 | static void (*my_sig_func) (void *signal_arg, int value); |
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203 | static void *my_sig_arg; |
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204 | |
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205 | void |
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206 | _attach (SV *loop_, IV sig_func, void *sig_arg) |
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207 | CODE: |
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208 | { |
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209 | my_sig_func = sig_func; |
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210 | my_sig_arg = sig_arg; |
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211 | |
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212 | /* now run the thread */ |
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213 | thread_create (&u->tid, l_run, 0); |
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214 | } |
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215 | |
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216 | And C<l_run> (the background thread) would eventually call the signaling |
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217 | function: |
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218 | |
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219 | my_sig_func (my_sig_arg, 0); |
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220 | |
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221 | You can have a look at L<EV::Loop::Async> for an actual example using |
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222 | intra-thread communication, locking and so on. |
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223 | |
146 | |
224 | |
147 | =head1 THE Async::Interrupt CLASS |
225 | =head1 THE Async::Interrupt CLASS |
148 | |
226 | |
149 | =over 4 |
227 | =over 4 |
150 | |
228 | |
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498 | |
576 | |
499 | =item $epipe->drain |
577 | =item $epipe->drain |
500 | |
578 | |
501 | Drain (empty) the pipe. |
579 | Drain (empty) the pipe. |
502 | |
580 | |
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581 | =item ($c_func, $c_arg) = $epipe->drain_func |
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582 | |
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583 | Returns a function pointer and C<void *> argument that can be called to |
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584 | have the effect of C<< $epipe->drain >> on the XS level. |
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585 | |
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586 | It has the following prototype and needs to be passed the specified |
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587 | C<$c_arg>, which is a C<void *> cast to C<IV>: |
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588 | |
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589 | void (*c_func) (void *c_arg) |
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590 | |
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591 | An example call would look like: |
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592 | |
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593 | c_func (c_arg); |
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594 | |
503 | =item $epipe->renew |
595 | =item $epipe->renew |
504 | |
596 | |
505 | Recreates the pipe (useful after a fork). The reading side will not change |
597 | Recreates the pipe (useful after a fork). The reading side will not change |
506 | it's file descriptor number, but the writing side might. |
598 | it's file descriptor number, but the writing side might. |
507 | |
599 | |
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600 | =item $epipe->wait |
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601 | |
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602 | This method blocks the process until there are events on the pipe. This is |
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603 | not a very event-based or ncie way of usign an event pipe, but it can be |
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604 | occasionally useful. |
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605 | |
508 | =back |
606 | =back |
509 | |
607 | |
510 | =cut |
608 | =cut |
511 | |
609 | |
512 | 1; |
610 | 1; |
513 | |
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514 | =head1 EXAMPLE |
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515 | |
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516 | There really should be a complete C/XS example. Bug me about it. Better |
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517 | yet, create one. |
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518 | |
611 | |
519 | =head1 IMPLEMENTATION DETAILS AND LIMITATIONS |
612 | =head1 IMPLEMENTATION DETAILS AND LIMITATIONS |
520 | |
613 | |
521 | This module works by "hijacking" SIGKILL, which is guaranteed to always |
614 | This module works by "hijacking" SIGKILL, which is guaranteed to always |
522 | exist, but also cannot be caught, so is always available. |
615 | exist, but also cannot be caught, so is always available. |