… | |
… | |
40 | points in your program, so locking and parallel access are rarely an |
40 | points in your program, so locking and parallel access are rarely an |
41 | issue, making thread programming much safer and easier than using other |
41 | issue, making thread programming much safer and easier than using other |
42 | thread models. |
42 | thread models. |
43 | |
43 | |
44 | Unlike the so-called "Perl threads" (which are not actually real threads |
44 | Unlike the so-called "Perl threads" (which are not actually real threads |
45 | but only the windows process emulation ported to unix, and as such act |
45 | but only the windows process emulation (see section of same name for |
46 | as processes), Coro provides a full shared address space, which makes |
46 | more details) ported to UNIX, and as such act as processes), Coro |
47 | communication between threads very easy. And Coro's threads are fast, |
47 | provides a full shared address space, which makes communication between |
48 | too: disabling the Windows process emulation code in your perl and using |
48 | threads very easy. And coro threads are fast, too: disabling the Windows |
49 | Coro can easily result in a two to four times speed increase for your |
49 | process emulation code in your perl and using Coro can easily result in |
50 | programs. A parallel matrix multiplication benchmark runs over 300 times |
50 | a two to four times speed increase for your programs. A parallel matrix |
|
|
51 | multiplication benchmark (very communication-intensive) runs over 300 |
51 | faster on a single core than perl's pseudo-threads on a quad core using |
52 | times faster on a single core than perls pseudo-threads on a quad core |
52 | all four cores. |
53 | using all four cores. |
53 | |
54 | |
54 | Coro achieves that by supporting multiple running interpreters that share |
55 | Coro achieves that by supporting multiple running interpreters that share |
55 | data, which is especially useful to code pseudo-parallel processes and |
56 | data, which is especially useful to code pseudo-parallel processes and |
56 | for event-based programming, such as multiple HTTP-GET requests running |
57 | for event-based programming, such as multiple HTTP-GET requests running |
57 | concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
58 | concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
… | |
… | |
63 | variables (see L<Coro::State> for more configuration and background info). |
64 | variables (see L<Coro::State> for more configuration and background info). |
64 | |
65 | |
65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
66 | See also the C<SEE ALSO> section at the end of this document - the Coro |
66 | module family is quite large. |
67 | module family is quite large. |
67 | |
68 | |
|
|
69 | =head1 CORO THREAD LIFE CYCLE |
|
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70 | |
|
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71 | During the long and exciting (or not) life of a coro thread, it goes |
|
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72 | through a number of states: |
|
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73 | |
|
|
74 | =over 4 |
|
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75 | |
|
|
76 | =item 1. Creation |
|
|
77 | |
|
|
78 | The first thing in the life of a coro thread is it's creation - |
|
|
79 | obviously. The typical way to create a thread is to call the C<async |
|
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80 | BLOCK> function: |
|
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81 | |
|
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82 | async { |
|
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83 | # thread code goes here |
|
|
84 | }; |
|
|
85 | |
|
|
86 | You can also pass arguments, which are put in C<@_>: |
|
|
87 | |
|
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88 | async { |
|
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89 | print $_[1]; # prints 2 |
|
|
90 | } 1, 2, 3; |
|
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91 | |
|
|
92 | This creates a new coro thread and puts it into the ready queue, meaning |
|
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93 | it will run as soon as the CPU is free for it. |
|
|
94 | |
|
|
95 | C<async> will return a Coro object - you can store this for future |
|
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96 | reference or ignore it - a thread that is running, ready to run or waiting |
|
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97 | for some event is alive on it's own. |
|
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98 | |
|
|
99 | Another way to create a thread is to call the C<new> constructor with a |
|
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100 | code-reference: |
|
|
101 | |
|
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102 | new Coro sub { |
|
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103 | # thread code goes here |
|
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104 | }, @optional_arguments; |
|
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105 | |
|
|
106 | This is quite similar to calling C<async>, but the important difference is |
|
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107 | that the new thread is not put into the ready queue, so the thread will |
|
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108 | not run until somebody puts it there. C<async> is, therefore, identical to |
|
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109 | this sequence: |
|
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110 | |
|
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111 | my $coro = new Coro sub { |
|
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112 | # thread code goes here |
|
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113 | }; |
|
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114 | $coro->ready; |
|
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115 | return $coro; |
|
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116 | |
|
|
117 | =item 2. Startup |
|
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118 | |
|
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119 | When a new coro thread is created, only a copy of the code reference |
|
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120 | and the arguments are stored, no extra memory for stacks and so on is |
|
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121 | allocated, keeping the coro thread in a low-memory state. |
|
|
122 | |
|
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123 | Only when it actually starts executing will all the resources be finally |
|
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124 | allocated. |
|
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125 | |
|
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126 | The optional arguments specified at coro creation are available in C<@_>, |
|
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127 | similar to function calls. |
|
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128 | |
|
|
129 | =item 3. Running / Blocking |
|
|
130 | |
|
|
131 | A lot can happen after the coro thread has started running. Quite usually, |
|
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132 | it will not run to the end in one go (because you could use a function |
|
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133 | instead), but it will give up the CPU regularly because it waits for |
|
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134 | external events. |
|
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135 | |
|
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136 | As long as a coro thread runs, its Coro object is available in the global |
|
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137 | variable C<$Coro::current>. |
|
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138 | |
|
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139 | The low-level way to give up the CPU is to call the scheduler, which |
|
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140 | selects a new coro thread to run: |
|
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141 | |
|
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142 | Coro::schedule; |
|
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143 | |
|
|
144 | Since running threads are not in the ready queue, calling the scheduler |
|
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145 | without doing anything else will block the coro thread forever - you need |
|
|
146 | to arrange either for the coro to put woken up (readied) by some other |
|
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147 | event or some other thread, or you can put it into the ready queue before |
|
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148 | scheduling: |
|
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149 | |
|
|
150 | # this is exactly what Coro::cede does |
|
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151 | $Coro::current->ready; |
|
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152 | Coro::schedule; |
|
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153 | |
|
|
154 | All the higher-level synchronisation methods (Coro::Semaphore, |
|
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155 | Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<< |
|
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156 | Coro::schedule >>. |
|
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157 | |
|
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158 | While the coro thread is running it also might get assigned a C-level |
|
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159 | thread, or the C-level thread might be unassigned from it, as the Coro |
|
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160 | runtime wishes. A C-level thread needs to be assigned when your perl |
|
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161 | thread calls into some C-level function and that function in turn calls |
|
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162 | perl and perl then wants to switch coroutines. This happens most often |
|
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163 | when you run an event loop and block in the callback, or when perl |
|
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164 | itself calls some function such as C<AUTOLOAD> or methods via the C<tie> |
|
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165 | mechanism. |
|
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166 | |
|
|
167 | =item 4. Termination |
|
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168 | |
|
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169 | Many threads actually terminate after some time. There are a number of |
|
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170 | ways to terminate a coro thread, the simplest is returning from the |
|
|
171 | top-level code reference: |
|
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172 | |
|
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173 | async { |
|
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174 | # after returning from here, the coro thread is terminated |
|
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175 | }; |
|
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176 | |
|
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177 | async { |
|
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178 | return if 0.5 < rand; # terminate a little earlier, maybe |
|
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179 | print "got a chance to print this\n"; |
|
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180 | # or here |
|
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181 | }; |
|
|
182 | |
|
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183 | Any values returned from the coroutine can be recovered using C<< ->join |
|
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184 | >>: |
|
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185 | |
|
|
186 | my $coro = async { |
|
|
187 | "hello, world\n" # return a string |
|
|
188 | }; |
|
|
189 | |
|
|
190 | my $hello_world = $coro->join; |
|
|
191 | |
|
|
192 | print $hello_world; |
|
|
193 | |
|
|
194 | Another way to terminate is to call C<< Coro::terminate >>, which at any |
|
|
195 | subroutine call nesting level: |
|
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196 | |
|
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197 | async { |
|
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198 | Coro::terminate "return value 1", "return value 2"; |
|
|
199 | }; |
|
|
200 | |
|
|
201 | And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the |
|
|
202 | coro thread from another thread: |
|
|
203 | |
|
|
204 | my $coro = async { |
|
|
205 | exit 1; |
|
|
206 | }; |
|
|
207 | |
|
|
208 | $coro->cancel; # also accepts values for ->join to retrieve |
|
|
209 | |
|
|
210 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
|
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211 | actually exiting, and might leave C libraries and XS modules in a weird |
|
|
212 | state. Unlike other thread implementations, however, Coro is exceptionally |
|
|
213 | safe with regards to cancellation, as perl will always be in a consistent |
|
|
214 | state, and for those cases where you want to do truly marvellous things |
|
|
215 | with your coro while it is being cancelled - that is, make sure all |
|
|
216 | cleanup code is executed from the thread being cancelled - there is even a |
|
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217 | C<< ->safe_cancel >> method. |
|
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218 | |
|
|
219 | So, cancelling a thread that runs in an XS event loop might not be the |
|
|
220 | best idea, but any other combination that deals with perl only (cancelling |
|
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221 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
|
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222 | safe. |
|
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223 | |
|
|
224 | Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
|
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225 | automatically - just like other objects in Perl. This is not such a common |
|
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226 | case, however - a running thread is referencedy b C<$Coro::current>, a |
|
|
227 | thread ready to run is referenced by the ready queue, a thread waiting |
|
|
228 | on a lock or semaphore is referenced by being in some wait list and so |
|
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229 | on. But a thread that isn't in any of those queues gets cancelled: |
|
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230 | |
|
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231 | async { |
|
|
232 | schedule; # cede to other coros, don't go into the ready queue |
|
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233 | }; |
|
|
234 | |
|
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235 | cede; |
|
|
236 | # now the async above is destroyed, as it is not referenced by anything. |
|
|
237 | |
|
|
238 | =item 5. Cleanup |
|
|
239 | |
|
|
240 | Threads will allocate various resources. Most but not all will be returned |
|
|
241 | when a thread terminates, during clean-up. |
|
|
242 | |
|
|
243 | Cleanup is quite similar to throwing an uncaught exception: perl will |
|
|
244 | work it's way up through all subroutine calls and blocks. On it's way, it |
|
|
245 | will release all C<my> variables, undo all C<local>'s and free any other |
|
|
246 | resources truly local to the thread. |
|
|
247 | |
|
|
248 | So, a common way to free resources is to keep them referenced only by my |
|
|
249 | variables: |
|
|
250 | |
|
|
251 | async { |
|
|
252 | my $big_cache = new Cache ...; |
|
|
253 | }; |
|
|
254 | |
|
|
255 | If there are no other references, then the C<$big_cache> object will be |
|
|
256 | freed when the thread terminates, regardless of how it does so. |
|
|
257 | |
|
|
258 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
|
|
259 | resources, but that's where the C<guard> methods come in handy: |
|
|
260 | |
|
|
261 | my $sem = new Coro::Semaphore; |
|
|
262 | |
|
|
263 | async { |
|
|
264 | my $lock_guard = $sem->guard; |
|
|
265 | # if we reutrn, or die or get cancelled, here, |
|
|
266 | # then the semaphore will be "up"ed. |
|
|
267 | }; |
|
|
268 | |
|
|
269 | The C<Guard::guard> function comes in handy for any custom cleanup you |
|
|
270 | might want to do (but you cannot switch to other coroutines form those |
|
|
271 | code blocks): |
|
|
272 | |
|
|
273 | async { |
|
|
274 | my $window = new Gtk2::Window "toplevel"; |
|
|
275 | # The window will not be cleaned up automatically, even when $window |
|
|
276 | # gets freed, so use a guard to ensure it's destruction |
|
|
277 | # in case of an error: |
|
|
278 | my $window_guard = Guard::guard { $window->destroy }; |
|
|
279 | |
|
|
280 | # we are safe here |
|
|
281 | }; |
|
|
282 | |
|
|
283 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
|
|
284 | replacing the coro thread description: |
|
|
285 | |
|
|
286 | sub myfunction { |
|
|
287 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
|
|
288 | |
|
|
289 | # if we return or die here, the description will be restored |
|
|
290 | } |
|
|
291 | |
|
|
292 | =item 6. Viva La Zombie Muerte |
|
|
293 | |
|
|
294 | Even after a thread has terminated and cleaned up its resources, the Coro |
|
|
295 | object still is there and stores the return values of the thread. |
|
|
296 | |
|
|
297 | The means the Coro object gets freed automatically when the thread has |
|
|
298 | terminated and cleaned up and there arenot other references. |
|
|
299 | |
|
|
300 | If there are, the Coro object will stay around, and you can call C<< |
|
|
301 | ->join >> as many times as you wish to retrieve the result values: |
|
|
302 | |
|
|
303 | async { |
|
|
304 | print "hi\n"; |
|
|
305 | 1 |
|
|
306 | }; |
|
|
307 | |
|
|
308 | # run the async above, and free everything before returning |
|
|
309 | # from Coro::cede: |
|
|
310 | Coro::cede; |
|
|
311 | |
|
|
312 | { |
|
|
313 | my $coro = async { |
|
|
314 | print "hi\n"; |
|
|
315 | 1 |
|
|
316 | }; |
|
|
317 | |
|
|
318 | # run the async above, and clean up, but do not free the coro |
|
|
319 | # object: |
|
|
320 | Coro::cede; |
|
|
321 | |
|
|
322 | # optionally retrieve the result values |
|
|
323 | my @results = $coro->join; |
|
|
324 | |
|
|
325 | # now $coro goes out of scope, and presumably gets freed |
|
|
326 | }; |
|
|
327 | |
|
|
328 | =back |
|
|
329 | |
68 | =cut |
330 | =cut |
69 | |
331 | |
70 | package Coro; |
332 | package Coro; |
71 | |
333 | |
72 | use strict qw(vars subs); |
334 | use common::sense; |
73 | no warnings "uninitialized"; |
335 | |
|
|
336 | use Carp (); |
74 | |
337 | |
75 | use Guard (); |
338 | use Guard (); |
76 | |
339 | |
77 | use Coro::State; |
340 | use Coro::State; |
78 | |
341 | |
… | |
… | |
80 | |
343 | |
81 | our $idle; # idle handler |
344 | our $idle; # idle handler |
82 | our $main; # main coro |
345 | our $main; # main coro |
83 | our $current; # current coro |
346 | our $current; # current coro |
84 | |
347 | |
85 | our $VERSION = 5.17; |
348 | our $VERSION = 5.372; |
86 | |
349 | |
87 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
350 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
88 | our %EXPORT_TAGS = ( |
351 | our %EXPORT_TAGS = ( |
89 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
352 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
90 | ); |
353 | ); |
91 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
354 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
92 | |
355 | |
… | |
… | |
123 | |
386 | |
124 | This variable is mainly useful to integrate Coro into event loops. It is |
387 | This variable is mainly useful to integrate Coro into event loops. It is |
125 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
388 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
126 | pretty low-level functionality. |
389 | pretty low-level functionality. |
127 | |
390 | |
128 | This variable stores either a Coro object or a callback. |
391 | This variable stores a Coro object that is put into the ready queue when |
|
|
392 | there are no other ready threads (without invoking any ready hooks). |
129 | |
393 | |
130 | If it is a callback, the it is called whenever the scheduler finds no |
394 | The default implementation dies with "FATAL: deadlock detected.", followed |
131 | ready coros to run. The default implementation prints "FATAL: |
395 | by a thread listing, because the program has no other way to continue. |
132 | deadlock detected" and exits, because the program has no other way to |
|
|
133 | continue. |
|
|
134 | |
|
|
135 | If it is a coro object, then this object will be readied (without |
|
|
136 | invoking any ready hooks, however) when the scheduler finds no other ready |
|
|
137 | coros to run. |
|
|
138 | |
396 | |
139 | This hook is overwritten by modules such as C<Coro::EV> and |
397 | This hook is overwritten by modules such as C<Coro::EV> and |
140 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
398 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
141 | coro so the scheduler can run it. |
399 | coro so the scheduler can run it. |
142 | |
400 | |
143 | Note that the callback I<must not>, under any circumstances, block |
|
|
144 | the current coro. Normally, this is achieved by having an "idle |
|
|
145 | coro" that calls the event loop and then blocks again, and then |
|
|
146 | readying that coro in the idle handler, or by simply placing the idle |
|
|
147 | coro in this variable. |
|
|
148 | |
|
|
149 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
401 | See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
150 | technique. |
|
|
151 | |
|
|
152 | Please note that if your callback recursively invokes perl (e.g. for event |
|
|
153 | handlers), then it must be prepared to be called recursively itself. |
|
|
154 | |
402 | |
155 | =cut |
403 | =cut |
156 | |
404 | |
157 | $idle = sub { |
405 | # ||= because other modules could have provided their own by now |
158 | require Carp; |
406 | $idle ||= new Coro sub { |
159 | Carp::croak ("FATAL: deadlock detected"); |
407 | require Coro::Debug; |
|
|
408 | die "FATAL: deadlock detected.\n" |
|
|
409 | . Coro::Debug::ps_listing (); |
160 | }; |
410 | }; |
161 | |
411 | |
162 | # this coro is necessary because a coro |
412 | # this coro is necessary because a coro |
163 | # cannot destroy itself. |
413 | # cannot destroy itself. |
164 | our @destroy; |
414 | our @destroy; |
165 | our $manager; |
415 | our $manager; |
166 | |
416 | |
167 | $manager = new Coro sub { |
417 | $manager = new Coro sub { |
168 | while () { |
418 | while () { |
169 | Coro::State::cancel shift @destroy |
419 | _destroy shift @destroy |
170 | while @destroy; |
420 | while @destroy; |
171 | |
421 | |
172 | &schedule; |
422 | &schedule; |
173 | } |
423 | } |
174 | }; |
424 | }; |
… | |
… | |
272 | =item schedule |
522 | =item schedule |
273 | |
523 | |
274 | Calls the scheduler. The scheduler will find the next coro that is |
524 | Calls the scheduler. The scheduler will find the next coro that is |
275 | to be run from the ready queue and switches to it. The next coro |
525 | to be run from the ready queue and switches to it. The next coro |
276 | to be run is simply the one with the highest priority that is longest |
526 | to be run is simply the one with the highest priority that is longest |
277 | in its ready queue. If there is no coro ready, it will clal the |
527 | in its ready queue. If there is no coro ready, it will call the |
278 | C<$Coro::idle> hook. |
528 | C<$Coro::idle> hook. |
279 | |
529 | |
280 | Please note that the current coro will I<not> be put into the ready |
530 | Please note that the current coro will I<not> be put into the ready |
281 | queue, so calling this function usually means you will never be called |
531 | queue, so calling this function usually means you will never be called |
282 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
532 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
… | |
… | |
308 | coro, regardless of priority. This is useful sometimes to ensure |
558 | coro, regardless of priority. This is useful sometimes to ensure |
309 | progress is made. |
559 | progress is made. |
310 | |
560 | |
311 | =item terminate [arg...] |
561 | =item terminate [arg...] |
312 | |
562 | |
313 | Terminates the current coro with the given status values (see L<cancel>). |
563 | Terminates the current coro with the given status values (see |
|
|
564 | L<cancel>). The values will not be copied, but referenced directly. |
314 | |
565 | |
315 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
566 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
316 | |
567 | |
317 | These function install enter and leave winders in the current scope. The |
568 | These function install enter and leave winders in the current scope. The |
318 | enter block will be executed when on_enter is called and whenever the |
569 | enter block will be executed when on_enter is called and whenever the |
… | |
… | |
474 | To avoid this, it is best to put a suspended coro into the ready queue |
725 | To avoid this, it is best to put a suspended coro into the ready queue |
475 | unconditionally, as every synchronisation mechanism must protect itself |
726 | unconditionally, as every synchronisation mechanism must protect itself |
476 | against spurious wakeups, and the one in the Coro family certainly do |
727 | against spurious wakeups, and the one in the Coro family certainly do |
477 | that. |
728 | that. |
478 | |
729 | |
|
|
730 | =item $state->is_new |
|
|
731 | |
|
|
732 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
733 | yet. Those states basically consist of only the code reference to call and |
|
|
734 | the arguments, but consumes very little other resources. New states will |
|
|
735 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
736 | |
|
|
737 | =item $state->is_zombie |
|
|
738 | |
|
|
739 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
740 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
741 | C<safe_cancel>'ed or simply went out of scope. |
|
|
742 | |
|
|
743 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
744 | exited and only stores and exit status and no other resources is called a |
|
|
745 | "zombie". |
|
|
746 | |
479 | =item $is_ready = $coro->is_ready |
747 | =item $is_ready = $coro->is_ready |
480 | |
748 | |
481 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
749 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
482 | object gets destroyed, it will eventually be scheduled by the scheduler. |
750 | object gets destroyed, it will eventually be scheduled by the scheduler. |
483 | |
751 | |
… | |
… | |
492 | Returns true iff this Coro object has been suspended. Suspended Coros will |
760 | Returns true iff this Coro object has been suspended. Suspended Coros will |
493 | not ever be scheduled. |
761 | not ever be scheduled. |
494 | |
762 | |
495 | =item $coro->cancel (arg...) |
763 | =item $coro->cancel (arg...) |
496 | |
764 | |
497 | Terminates the given Coro and makes it return the given arguments as |
765 | Terminates the given Coro thread and makes it return the given arguments as |
498 | status (default: the empty list). Never returns if the Coro is the |
766 | status (default: an empty list). Never returns if the Coro is the |
499 | current Coro. |
767 | current Coro. |
500 | |
768 | |
501 | =cut |
769 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
770 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
771 | bad things can happen, or if the cancelled thread insists on running |
|
|
772 | complicated cleanup handlers that rely on it'S thread context, things will |
|
|
773 | not work. |
502 | |
774 | |
503 | sub cancel { |
775 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
504 | my $self = shift; |
776 | a thread context, and is not allowed to switch to other threads. On the |
|
|
777 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
778 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
779 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
780 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
505 | |
781 | |
506 | if ($current == $self) { |
782 | The arguments to C<< ->cancel >> are not copied, but instead will |
507 | terminate @_; |
783 | be referenced directly (e.g. if you pass C<$var> and after the call |
508 | } else { |
784 | change that variable, then you might change the return values passed to |
509 | $self->{_status} = [@_]; |
785 | e.g. C<join>, so don't do that). |
510 | Coro::State::cancel $self; |
786 | |
|
|
787 | The resources of the Coro are usually freed (or destructed) before this |
|
|
788 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
789 | in some cases the manager thread has to run first to actually destruct the |
|
|
790 | Coro object. |
|
|
791 | |
|
|
792 | =item $coro->safe_cancel ($arg...) |
|
|
793 | |
|
|
794 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
795 | consequently, can fail with an exception in cases the thread is not in a |
|
|
796 | cancellable state. |
|
|
797 | |
|
|
798 | This method works a bit like throwing an exception that cannot be caught |
|
|
799 | - specifically, it will clean up the thread from within itself, so |
|
|
800 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
801 | context and can block if they wish. The downside is that there is no |
|
|
802 | guarantee that the thread can be cancelled when you call this method, and |
|
|
803 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
804 | C<terminate>. |
|
|
805 | |
|
|
806 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
807 | or it has no C context attached and is inside an SLF function. |
|
|
808 | |
|
|
809 | The latter two basically mean that the thread isn't currently inside a |
|
|
810 | perl callback called from some C function (usually via some XS modules) |
|
|
811 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
812 | API). |
|
|
813 | |
|
|
814 | This call returns true when it could cancel the thread, or croaks with an |
|
|
815 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
816 | |
|
|
817 | Why the weird interface? Well, there are two common models on how and |
|
|
818 | when to cancel things. In the first, you have the expectation that your |
|
|
819 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
820 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
821 | croaks to notify of the bug. |
|
|
822 | |
|
|
823 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
824 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
825 | relatively easy like this: |
|
|
826 | |
|
|
827 | if (! eval { $coro->safe_cancel }) { |
|
|
828 | warn "unable to cancel thread: $@"; |
511 | } |
829 | } |
512 | } |
830 | |
|
|
831 | However, what you never should do is first try to cancel "safely" and |
|
|
832 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
833 | no sense: either you rely on being able to execute cleanup code in your |
|
|
834 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
835 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
836 | direct. |
513 | |
837 | |
514 | =item $coro->schedule_to |
838 | =item $coro->schedule_to |
515 | |
839 | |
516 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
840 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
517 | of continuing with the next coro from the ready queue, always switch to |
841 | of continuing with the next coro from the ready queue, always switch to |
… | |
… | |
536 | inside the coro at the next convenient point in time. Otherwise |
860 | inside the coro at the next convenient point in time. Otherwise |
537 | clears the exception object. |
861 | clears the exception object. |
538 | |
862 | |
539 | Coro will check for the exception each time a schedule-like-function |
863 | Coro will check for the exception each time a schedule-like-function |
540 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
864 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
541 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
865 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
542 | detect this case and return early in case an exception is pending. |
866 | that are part of Coro itself) detect this case and return early in case an |
|
|
867 | exception is pending. |
543 | |
868 | |
544 | The exception object will be thrown "as is" with the specified scalar in |
869 | The exception object will be thrown "as is" with the specified scalar in |
545 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
870 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
546 | (unlike with C<die>). |
871 | (unlike with C<die>). |
547 | |
872 | |
548 | This can be used as a softer means than C<cancel> to ask a coro to |
873 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
549 | end itself, although there is no guarantee that the exception will lead to |
874 | >to ask a coro to end itself, although there is no guarantee that the |
550 | termination, and if the exception isn't caught it might well end the whole |
875 | exception will lead to termination, and if the exception isn't caught it |
551 | program. |
876 | might well end the whole program. |
552 | |
877 | |
553 | You might also think of C<throw> as being the moral equivalent of |
878 | You might also think of C<throw> as being the moral equivalent of |
554 | C<kill>ing a coro with a signal (in this case, a scalar). |
879 | C<kill>ing a coro with a signal (in this case, a scalar). |
555 | |
880 | |
556 | =item $coro->join |
881 | =item $coro->join |
557 | |
882 | |
558 | Wait until the coro terminates and return any values given to the |
883 | Wait until the coro terminates and return any values given to the |
559 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
884 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
560 | from multiple coro, and all will be resumed and given the status |
885 | from multiple threads, and all will be resumed and given the status |
561 | return once the C<$coro> terminates. |
886 | return once the C<$coro> terminates. |
562 | |
887 | |
563 | =cut |
|
|
564 | |
|
|
565 | sub join { |
|
|
566 | my $self = shift; |
|
|
567 | |
|
|
568 | unless ($self->{_status}) { |
|
|
569 | my $current = $current; |
|
|
570 | |
|
|
571 | push @{$self->{_on_destroy}}, sub { |
|
|
572 | $current->ready; |
|
|
573 | undef $current; |
|
|
574 | }; |
|
|
575 | |
|
|
576 | &schedule while $current; |
|
|
577 | } |
|
|
578 | |
|
|
579 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
580 | } |
|
|
581 | |
|
|
582 | =item $coro->on_destroy (\&cb) |
888 | =item $coro->on_destroy (\&cb) |
583 | |
889 | |
584 | Registers a callback that is called when this coro gets destroyed, |
890 | Registers a callback that is called when this coro thread gets destroyed, |
585 | but before it is joined. The callback gets passed the terminate arguments, |
891 | that is, after it's resources have been freed but before it is joined. The |
|
|
892 | callback gets passed the terminate/cancel arguments, if any, and I<must |
586 | if any, and I<must not> die, under any circumstances. |
893 | not> die, under any circumstances. |
587 | |
894 | |
588 | =cut |
895 | There can be any number of C<on_destroy> callbacks per coro, and there is |
589 | |
896 | no way currently to remove a callback once added. |
590 | sub on_destroy { |
|
|
591 | my ($self, $cb) = @_; |
|
|
592 | |
|
|
593 | push @{ $self->{_on_destroy} }, $cb; |
|
|
594 | } |
|
|
595 | |
897 | |
596 | =item $oldprio = $coro->prio ($newprio) |
898 | =item $oldprio = $coro->prio ($newprio) |
597 | |
899 | |
598 | Sets (or gets, if the argument is missing) the priority of the |
900 | Sets (or gets, if the argument is missing) the priority of the |
599 | coro. Higher priority coro get run before lower priority |
901 | coro thread. Higher priority coro get run before lower priority |
600 | coro. Priorities are small signed integers (currently -4 .. +3), |
902 | coros. Priorities are small signed integers (currently -4 .. +3), |
601 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
903 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
602 | to get then): |
904 | to get then): |
603 | |
905 | |
604 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
906 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
605 | 3 > 1 > 0 > -1 > -3 > -4 |
907 | 3 > 1 > 0 > -1 > -3 > -4 |
606 | |
908 | |
607 | # set priority to HIGH |
909 | # set priority to HIGH |
608 | current->prio (PRIO_HIGH); |
910 | current->prio (PRIO_HIGH); |
609 | |
911 | |
610 | The idle coro ($Coro::idle) always has a lower priority than any |
912 | The idle coro thread ($Coro::idle) always has a lower priority than any |
611 | existing coro. |
913 | existing coro. |
612 | |
914 | |
613 | Changing the priority of the current coro will take effect immediately, |
915 | Changing the priority of the current coro will take effect immediately, |
614 | but changing the priority of coro in the ready queue (but not |
916 | but changing the priority of a coro in the ready queue (but not running) |
615 | running) will only take effect after the next schedule (of that |
917 | will only take effect after the next schedule (of that coro). This is a |
616 | coro). This is a bug that will be fixed in some future version. |
918 | bug that will be fixed in some future version. |
617 | |
919 | |
618 | =item $newprio = $coro->nice ($change) |
920 | =item $newprio = $coro->nice ($change) |
619 | |
921 | |
620 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
922 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
621 | higher values mean lower priority, just as in unix). |
923 | higher values mean lower priority, just as in UNIX's nice command). |
622 | |
924 | |
623 | =item $olddesc = $coro->desc ($newdesc) |
925 | =item $olddesc = $coro->desc ($newdesc) |
624 | |
926 | |
625 | Sets (or gets in case the argument is missing) the description for this |
927 | Sets (or gets in case the argument is missing) the description for this |
626 | coro. This is just a free-form string you can associate with a |
928 | coro thread. This is just a free-form string you can associate with a |
627 | coro. |
929 | coro. |
628 | |
930 | |
629 | This method simply sets the C<< $coro->{desc} >> member to the given |
931 | This method simply sets the C<< $coro->{desc} >> member to the given |
630 | string. You can modify this member directly if you wish. |
932 | string. You can modify this member directly if you wish, and in fact, this |
|
|
933 | is often preferred to indicate major processing states that cna then be |
|
|
934 | seen for example in a L<Coro::Debug> session: |
|
|
935 | |
|
|
936 | sub my_long_function { |
|
|
937 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
938 | ... |
|
|
939 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
940 | ... |
|
|
941 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
942 | ... |
|
|
943 | } |
631 | |
944 | |
632 | =cut |
945 | =cut |
633 | |
946 | |
634 | sub desc { |
947 | sub desc { |
635 | my $old = $_[0]{desc}; |
948 | my $old = $_[0]{desc}; |
… | |
… | |
672 | returning a new coderef. Unblocking means that calling the new coderef |
985 | returning a new coderef. Unblocking means that calling the new coderef |
673 | will return immediately without blocking, returning nothing, while the |
986 | will return immediately without blocking, returning nothing, while the |
674 | original code ref will be called (with parameters) from within another |
987 | original code ref will be called (with parameters) from within another |
675 | coro. |
988 | coro. |
676 | |
989 | |
677 | The reason this function exists is that many event libraries (such as the |
990 | The reason this function exists is that many event libraries (such as |
678 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
991 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
679 | of reentrancy). This means you must not block within event callbacks, |
992 | of reentrancy). This means you must not block within event callbacks, |
680 | otherwise you might suffer from crashes or worse. The only event library |
993 | otherwise you might suffer from crashes or worse. The only event library |
681 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
994 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
995 | you might still run into deadlocks if all event loops are blocked). |
|
|
996 | |
|
|
997 | Coro will try to catch you when you block in the event loop |
|
|
998 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
999 | only works when you do not run your own event loop. |
682 | |
1000 | |
683 | This function allows your callbacks to block by executing them in another |
1001 | This function allows your callbacks to block by executing them in another |
684 | coro where it is safe to block. One example where blocking is handy |
1002 | coro where it is safe to block. One example where blocking is handy |
685 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1003 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
686 | disk, for example. |
1004 | disk, for example. |
… | |
… | |
728 | unshift @unblock_queue, [$cb, @_]; |
1046 | unshift @unblock_queue, [$cb, @_]; |
729 | $unblock_scheduler->ready; |
1047 | $unblock_scheduler->ready; |
730 | } |
1048 | } |
731 | } |
1049 | } |
732 | |
1050 | |
733 | =item $cb = Coro::rouse_cb |
1051 | =item $cb = rouse_cb |
734 | |
1052 | |
735 | Create and return a "rouse callback". That's a code reference that, |
1053 | Create and return a "rouse callback". That's a code reference that, |
736 | when called, will remember a copy of its arguments and notify the owner |
1054 | when called, will remember a copy of its arguments and notify the owner |
737 | coro of the callback. |
1055 | coro of the callback. |
738 | |
1056 | |
739 | See the next function. |
1057 | See the next function. |
740 | |
1058 | |
741 | =item @args = Coro::rouse_wait [$cb] |
1059 | =item @args = rouse_wait [$cb] |
742 | |
1060 | |
743 | Wait for the specified rouse callback (or the last one that was created in |
1061 | Wait for the specified rouse callback (or the last one that was created in |
744 | this coro). |
1062 | this coro). |
745 | |
1063 | |
746 | As soon as the callback is invoked (or when the callback was invoked |
1064 | As soon as the callback is invoked (or when the callback was invoked |
… | |
… | |
752 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
1070 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
753 | |
1071 | |
754 | =back |
1072 | =back |
755 | |
1073 | |
756 | =cut |
1074 | =cut |
|
|
1075 | |
|
|
1076 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1077 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1078 | |
|
|
1079 | *{"Coro::$module\::new"} = sub { |
|
|
1080 | require "Coro/$module.pm"; |
|
|
1081 | |
|
|
1082 | # some modules have their new predefined in State.xs, some don't |
|
|
1083 | *{"Coro::$module\::new"} = $old |
|
|
1084 | if $old; |
|
|
1085 | |
|
|
1086 | goto &{"Coro::$module\::new"}; |
|
|
1087 | }; |
|
|
1088 | } |
757 | |
1089 | |
758 | 1; |
1090 | 1; |
759 | |
1091 | |
760 | =head1 HOW TO WAIT FOR A CALLBACK |
1092 | =head1 HOW TO WAIT FOR A CALLBACK |
761 | |
1093 | |
… | |
… | |
841 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1173 | future to allow per-thread schedulers, but Coro::State does not yet allow |
842 | this). I recommend disabling thread support and using processes, as having |
1174 | this). I recommend disabling thread support and using processes, as having |
843 | the windows process emulation enabled under unix roughly halves perl |
1175 | the windows process emulation enabled under unix roughly halves perl |
844 | performance, even when not used. |
1176 | performance, even when not used. |
845 | |
1177 | |
|
|
1178 | Attempts to use threads created in another emulated process will crash |
|
|
1179 | ("cleanly", with a null pointer exception). |
|
|
1180 | |
846 | =item coro switching is not signal safe |
1181 | =item coro switching is not signal safe |
847 | |
1182 | |
848 | You must not switch to another coro from within a signal handler |
1183 | You must not switch to another coro from within a signal handler (only |
849 | (only relevant with %SIG - most event libraries provide safe signals). |
1184 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1185 | you are sure you are not interrupting a Coro function. |
850 | |
1186 | |
851 | That means you I<MUST NOT> call any function that might "block" the |
1187 | That means you I<MUST NOT> call any function that might "block" the |
852 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1188 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
853 | anything that calls those. Everything else, including calling C<ready>, |
1189 | anything that calls those. Everything else, including calling C<ready>, |
854 | works. |
1190 | works. |
855 | |
1191 | |
856 | =back |
1192 | =back |
857 | |
1193 | |
858 | |
1194 | |
|
|
1195 | =head1 WINDOWS PROCESS EMULATION |
|
|
1196 | |
|
|
1197 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1198 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1199 | while in the same mail making rather confused statements about perl |
|
|
1200 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1201 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1202 | it is probably not obvious to everybody). |
|
|
1203 | |
|
|
1204 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1205 | scripting languages given on the perl workshop 2009: |
|
|
1206 | |
|
|
1207 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1208 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1209 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1210 | |
|
|
1211 | It does that by using threads instead of OS processes. The difference |
|
|
1212 | between processes and threads is that threads share memory (and other |
|
|
1213 | state, such as files) between threads within a single process, while |
|
|
1214 | processes do not share anything (at least not semantically). That |
|
|
1215 | means that modifications done by one thread are seen by others, while |
|
|
1216 | modifications by one process are not seen by other processes. |
|
|
1217 | |
|
|
1218 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1219 | process, all state is copied (memory is copied physically, files and code |
|
|
1220 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1221 | the same behaviour can be achieved by using operating system processes, |
|
|
1222 | except that UNIX typically uses hardware built into the system to do this |
|
|
1223 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1224 | software (rather efficiently, but of course it is still much slower than |
|
|
1225 | dedicated hardware). |
|
|
1226 | |
|
|
1227 | As mentioned before, loading code, modifying code, modifying data |
|
|
1228 | structures and so on is only visible in the ithreads process doing the |
|
|
1229 | modification, not in other ithread processes within the same OS process. |
|
|
1230 | |
|
|
1231 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1232 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1233 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1234 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1235 | faster). |
|
|
1236 | |
|
|
1237 | Sharing data is in the i-threads model is done by transfering data |
|
|
1238 | structures between threads using copying semantics, which is very slow - |
|
|
1239 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1240 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1241 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1242 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1243 | real threads, refer to my talk for details). |
|
|
1244 | |
|
|
1245 | As summary, i-threads *use* threads to implement processes, while |
|
|
1246 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1247 | processes. I-threads slow down every perl program when enabled, and |
|
|
1248 | outside of windows, serve no (or little) practical purpose, but |
|
|
1249 | disadvantages every single-threaded Perl program. |
|
|
1250 | |
|
|
1251 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1252 | misleading as it implies that it implements some kind of thread model for |
|
|
1253 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1254 | actual use and behaviour of it much better. |
|
|
1255 | |
859 | =head1 SEE ALSO |
1256 | =head1 SEE ALSO |
860 | |
1257 | |
861 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1258 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
862 | |
1259 | |
863 | Debugging: L<Coro::Debug>. |
1260 | Debugging: L<Coro::Debug>. |