… | |
… | |
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 USAGE EXAMPLES |
|
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97 | |
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98 | =head2 Implementing race-free signal handling |
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99 | |
|
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100 | This example uses a single event pipe for all signals, and one |
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101 | Async::Interrupt per signal. This code is actually what the L<AnyEvent> |
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102 | module uses itself when Async::Interrupt is available. |
|
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103 | |
|
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104 | First, create the event pipe and hook it into the event loop |
|
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105 | |
|
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106 | $SIGPIPE = new Async::Interrupt::EventPipe; |
|
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107 | $SIGPIPE_W = AnyEvent->io ( |
|
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108 | fh => $SIGPIPE->fileno, |
|
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109 | poll => "r", |
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110 | cb => \&_signal_check, # defined later |
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111 | ); |
|
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112 | |
|
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113 | Then, for each signal to hook, create an Async::Interrupt object. The |
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114 | callback just sets a global variable, as we are only interested in |
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115 | synchronous signals (i.e. when the event loop polls), which is why the |
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116 | pipe draining is not done automatically. |
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117 | |
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118 | my $interrupt = new Async::Interrupt |
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119 | cb => sub { undef $SIGNAL_RECEIVED{$signum} } |
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120 | signal => $signum, |
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121 | pipe => [$SIGPIPE->filenos], |
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122 | pipe_autodrain => 0, |
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123 | ; |
|
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124 | |
|
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125 | Finally, the I/O callback for the event pipe handles the signals: |
|
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126 | |
|
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127 | sub _signal_check { |
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128 | # drain the pipe first |
|
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129 | $SIGPIPE->drain; |
|
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130 | |
|
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131 | # two loops, just to be sure |
|
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132 | while (%SIGNAL_RECEIVED) { |
|
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133 | for (keys %SIGNAL_RECEIVED) { |
|
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134 | delete $SIGNAL_RECEIVED{$_}; |
|
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135 | warn "signal $_ received\n"; |
|
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136 | } |
|
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137 | } |
|
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138 | } |
|
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139 | |
|
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140 | =head2 Interrupt perl from another thread |
|
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141 | |
|
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142 | This example interrupts the Perl interpreter from another thread, via the |
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143 | XS API. This is used by e.g. the L<EV::Loop::Async> module. |
|
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144 | |
|
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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 | |
|
|
224 | |
93 | =head1 THE Async::Interrupt CLASS |
225 | =head1 THE Async::Interrupt CLASS |
94 | |
226 | |
95 | =over 4 |
227 | =over 4 |
96 | |
228 | |
97 | =cut |
229 | =cut |
… | |
… | |
100 | |
232 | |
101 | use common::sense; |
233 | use common::sense; |
102 | |
234 | |
103 | BEGIN { |
235 | BEGIN { |
104 | # the next line forces initialisation of internal |
236 | # the next line forces initialisation of internal |
105 | # signal handling # variables |
237 | # signal handling variables, otherwise, PL_sig_pending |
|
|
238 | # etc. will be null pointers. |
106 | $SIG{KILL} = sub { }; |
239 | $SIG{KILL} = sub { }; |
107 | |
240 | |
108 | our $VERSION = '0.6'; |
241 | our $VERSION = '1.04'; |
109 | |
242 | |
110 | require XSLoader; |
243 | require XSLoader; |
111 | XSLoader::load ("Async::Interrupt", $VERSION); |
244 | XSLoader::load ("Async::Interrupt", $VERSION); |
112 | } |
245 | } |
113 | |
246 | |
… | |
… | |
136 | The exceptions are C<$!> and C<$@>, which are saved and restored by |
269 | The exceptions are C<$!> and C<$@>, which are saved and restored by |
137 | Async::Interrupt. |
270 | Async::Interrupt. |
138 | |
271 | |
139 | If the callback should throw an exception, then it will be caught, |
272 | If the callback should throw an exception, then it will be caught, |
140 | and C<$Async::Interrupt::DIED> will be called with C<$@> containing |
273 | and C<$Async::Interrupt::DIED> will be called with C<$@> containing |
141 | the exception. The default will simply C<warn> about the message and |
274 | the exception. The default will simply C<warn> about the message and |
142 | continue. |
275 | continue. |
143 | |
276 | |
144 | =item c_cb => [$c_func, $c_arg] |
277 | =item c_cb => [$c_func, $c_arg] |
145 | |
278 | |
146 | Registers a C callback the be invoked whenever the async interrupt is |
279 | Registers a C callback the be invoked whenever the async interrupt is |
… | |
… | |
162 | which case the requirements set out for C<cb> apply as well). |
295 | which case the requirements set out for C<cb> apply as well). |
163 | |
296 | |
164 | =item var => $scalar_ref |
297 | =item var => $scalar_ref |
165 | |
298 | |
166 | When specified, then the given argument must be a reference to a |
299 | When specified, then the given argument must be a reference to a |
167 | scalar. The scalar will be set to C<0> intiially. Signalling the interrupt |
300 | scalar. The scalar will be set to C<0> initially. Signalling the interrupt |
168 | object will set it to the passed value, handling the interrupt will reset |
301 | object will set it to the passed value, handling the interrupt will reset |
169 | it to C<0> again. |
302 | it to C<0> again. |
170 | |
303 | |
171 | Note that the only thing you are legally allowed to do is to is to check |
304 | Note that the only thing you are legally allowed to do is to is to check |
172 | the variable in a boolean or integer context (e.g. comparing it with a |
305 | the variable in a boolean or integer context (e.g. comparing it with a |
… | |
… | |
179 | given signal, that is, it will effectively call C<< ->signal (0) >> each time |
312 | given signal, that is, it will effectively call C<< ->signal (0) >> each time |
180 | the given signal is caught by the process. |
313 | the given signal is caught by the process. |
181 | |
314 | |
182 | Only one async can hook a given signal, and the signal will be restored to |
315 | Only one async can hook a given signal, and the signal will be restored to |
183 | defaults when the Async::Interrupt object gets destroyed. |
316 | defaults when the Async::Interrupt object gets destroyed. |
|
|
317 | |
|
|
318 | =item signal_hysteresis => $boolean |
|
|
319 | |
|
|
320 | Sets the initial signal hysteresis state, see the C<signal_hysteresis> |
|
|
321 | method, below. |
184 | |
322 | |
185 | =item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing] |
323 | =item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing] |
186 | |
324 | |
187 | Specifies two file descriptors (or file handles) that should be signalled |
325 | Specifies two file descriptors (or file handles) that should be signalled |
188 | whenever the async interrupt is signalled. This means a single octet will |
326 | whenever the async interrupt is signalled. This means a single octet will |
… | |
… | |
202 | |
340 | |
203 | If you want to share a single event pipe between multiple Async::Interrupt |
341 | If you want to share a single event pipe between multiple Async::Interrupt |
204 | objects, you can use the C<Async::Interrupt::EventPipe> class to manage |
342 | objects, you can use the C<Async::Interrupt::EventPipe> class to manage |
205 | those. |
343 | those. |
206 | |
344 | |
|
|
345 | =item pipe_autodrain => $boolean |
|
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346 | |
|
|
347 | Sets the initial autodrain state, see the C<pipe_autodrain> method, below. |
|
|
348 | |
207 | =back |
349 | =back |
208 | |
350 | |
209 | =cut |
351 | =cut |
210 | |
352 | |
211 | sub new { |
353 | sub new { |
212 | my ($class, %arg) = @_; |
354 | my ($class, %arg) = @_; |
213 | |
355 | |
214 | bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class |
356 | my $self = bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class; |
|
|
357 | |
|
|
358 | # urgs, reminds me of Event |
|
|
359 | for my $attr (qw(pipe_autodrain signal_hysteresis)) { |
|
|
360 | $self->$attr ($arg{$attr}) if exists $arg{$attr}; |
|
|
361 | } |
|
|
362 | |
|
|
363 | $self |
215 | } |
364 | } |
216 | |
365 | |
217 | =item ($signal_func, $signal_arg) = $async->signal_func |
366 | =item ($signal_func, $signal_arg) = $async->signal_func |
218 | |
367 | |
219 | Returns the address of a function to call asynchronously. The function has |
368 | Returns the address of a function to call asynchronously. The function |
220 | the following prototype and needs to be passed the specified C<$c_arg>, |
369 | has the following prototype and needs to be passed the specified |
221 | which is a C<void *> cast to C<IV>: |
370 | C<$signal_arg>, which is a C<void *> cast to C<IV>: |
222 | |
371 | |
223 | void (*signal_func) (void *signal_arg, int value) |
372 | void (*signal_func) (void *signal_arg, int value) |
224 | |
373 | |
225 | An example call would look like: |
374 | An example call would look like: |
226 | |
375 | |
… | |
… | |
264 | ; // do something |
413 | ; // do something |
265 | |
414 | |
266 | =item $async->signal ($value=1) |
415 | =item $async->signal ($value=1) |
267 | |
416 | |
268 | This signals the given async object from Perl code. Semi-obviously, this |
417 | This signals the given async object from Perl code. Semi-obviously, this |
269 | will instantly trigger the callback invocation. |
418 | will instantly trigger the callback invocation (it does not, as the name |
|
|
419 | might imply, do anything with POSIX signals). |
270 | |
420 | |
271 | C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0> |
421 | C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0> |
272 | (1..127 is portable). |
422 | (1..127 is portable). |
|
|
423 | |
|
|
424 | =item $async->signal_hysteresis ($enable) |
|
|
425 | |
|
|
426 | Enables or disables signal hysteresis (default: disabled). If a POSIX |
|
|
427 | signal is used as a signal source for the interrupt object, then enabling |
|
|
428 | signal hysteresis causes Async::Interrupt to reset the signal action to |
|
|
429 | C<SIG_IGN> in the signal handler and restore it just before handling the |
|
|
430 | interruption. |
|
|
431 | |
|
|
432 | When you expect a lot of signals (e.g. when using SIGIO), then enabling |
|
|
433 | signal hysteresis can reduce the number of handler invocations |
|
|
434 | considerably, at the cost of two extra syscalls. |
|
|
435 | |
|
|
436 | Note that setting the signal to C<SIG_IGN> can have unintended side |
|
|
437 | effects when you fork and exec other programs, as often they do nto expect |
|
|
438 | signals to be ignored by default. |
273 | |
439 | |
274 | =item $async->block |
440 | =item $async->block |
275 | |
441 | |
276 | =item $async->unblock |
442 | =item $async->unblock |
277 | |
443 | |
… | |
… | |
292 | This call C<< $async->block >> and installs a handler that is called when |
458 | This call C<< $async->block >> and installs a handler that is called when |
293 | the current scope is exited (via an exception, by canceling the Coro |
459 | the current scope is exited (via an exception, by canceling the Coro |
294 | thread, by calling last/goto etc.). |
460 | thread, by calling last/goto etc.). |
295 | |
461 | |
296 | This is the recommended (and fastest) way to implement critical sections. |
462 | This is the recommended (and fastest) way to implement critical sections. |
|
|
463 | |
|
|
464 | =item ($block_func, $block_arg) = $async->scope_block_func |
|
|
465 | |
|
|
466 | Returns the address of a function that implements the C<scope_block> |
|
|
467 | functionality. |
|
|
468 | |
|
|
469 | It has the following prototype and needs to be passed the specified |
|
|
470 | C<$block_arg>, which is a C<void *> cast to C<IV>: |
|
|
471 | |
|
|
472 | void (*block_func) (void *block_arg) |
|
|
473 | |
|
|
474 | An example call would look like: |
|
|
475 | |
|
|
476 | block_func (block_arg); |
|
|
477 | |
|
|
478 | The function is safe to call only from within the toplevel of a perl XS |
|
|
479 | function and will call C<LEAVE> and C<ENTER> (in this order!). |
297 | |
480 | |
298 | =item $async->pipe_enable |
481 | =item $async->pipe_enable |
299 | |
482 | |
300 | =item $async->pipe_disable |
483 | =item $async->pipe_disable |
301 | |
484 | |
… | |
… | |
339 | This only works when the pipe was created by Async::Interrupt. |
522 | This only works when the pipe was created by Async::Interrupt. |
340 | |
523 | |
341 | Async::Interrupt ensures that the reading file descriptor does not change |
524 | Async::Interrupt ensures that the reading file descriptor does not change |
342 | it's value. |
525 | it's value. |
343 | |
526 | |
|
|
527 | =item $signum = Async::Interrupt::sig2num $signame_or_number |
|
|
528 | |
|
|
529 | =item $signame = Async::Interrupt::sig2name $signame_or_number |
|
|
530 | |
|
|
531 | These two convenience functions simply convert a signal name or number to |
|
|
532 | the corresponding name or number. They are not used by this module and |
|
|
533 | exist just because perl doesn't have a nice way to do this on its own. |
|
|
534 | |
|
|
535 | They will return C<undef> on illegal names or numbers. |
|
|
536 | |
344 | =back |
537 | =back |
345 | |
538 | |
346 | =head1 THE Async::Interrupt::EventPipe CLASS |
539 | =head1 THE Async::Interrupt::EventPipe CLASS |
347 | |
540 | |
348 | Pipes are the predominent utility to make asynchronous signals |
541 | Pipes are the predominant utility to make asynchronous signals |
349 | synchronous. However, pipes are hard to come by: they don't exist on the |
542 | synchronous. However, pipes are hard to come by: they don't exist on the |
350 | broken windows platform, and on GNU/Linux systems, you might want to use |
543 | broken windows platform, and on GNU/Linux systems, you might want to use |
351 | an C<eventfd> instead. |
544 | an C<eventfd> instead. |
352 | |
545 | |
353 | This class creates selectable event pipes in a portable fashion: on |
546 | This class creates selectable event pipes in a portable fashion: on |
… | |
… | |
383 | |
576 | |
384 | =item $epipe->drain |
577 | =item $epipe->drain |
385 | |
578 | |
386 | Drain (empty) the pipe. |
579 | Drain (empty) the pipe. |
387 | |
580 | |
|
|
581 | =item ($c_func, $c_arg) = $epipe->drain_func |
|
|
582 | |
|
|
583 | Returns a function pointer and C<void *> argument that can be called to |
|
|
584 | have the effect of C<< $epipe->drain >> on the XS level. |
|
|
585 | |
|
|
586 | It has the following prototype and needs to be passed the specified |
|
|
587 | C<$c_arg>, which is a C<void *> cast to C<IV>: |
|
|
588 | |
|
|
589 | void (*c_func) (void *c_arg) |
|
|
590 | |
|
|
591 | An example call would look like: |
|
|
592 | |
|
|
593 | c_func (c_arg); |
|
|
594 | |
388 | =item $epipe->renew |
595 | =item $epipe->renew |
389 | |
596 | |
390 | 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 |
391 | it's file descriptor number, but the writing side might. |
598 | it's file descriptor number, but the writing side might. |
392 | |
599 | |
|
|
600 | =item $epipe->wait |
|
|
601 | |
|
|
602 | This method blocks the process until there are events on the pipe. This is |
|
|
603 | not a very event-based or ncie way of usign an event pipe, but it can be |
|
|
604 | occasionally useful. |
|
|
605 | |
393 | =back |
606 | =back |
394 | |
607 | |
395 | =cut |
608 | =cut |
396 | |
609 | |
397 | 1; |
610 | 1; |
398 | |
|
|
399 | =head1 EXAMPLE |
|
|
400 | |
|
|
401 | There really should be a complete C/XS example. Bug me about it. Better |
|
|
402 | yet, create one. |
|
|
403 | |
611 | |
404 | =head1 IMPLEMENTATION DETAILS AND LIMITATIONS |
612 | =head1 IMPLEMENTATION DETAILS AND LIMITATIONS |
405 | |
613 | |
406 | This module works by "hijacking" SIGKILL, which is guaranteed to always |
614 | This module works by "hijacking" SIGKILL, which is guaranteed to always |
407 | exist, but also cannot be caught, so is always available. |
615 | exist, but also cannot be caught, so is always available. |