… | |
… | |
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 | |
|
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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 | |
|
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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 - |
|
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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<@_>: |
|
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87 | |
|
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88 | async { |
|
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89 | print $_[1]; # prints 2 |
|
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90 | } 1, 2, 3; |
|
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91 | |
|
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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. |
|
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94 | |
|
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95 | C<async> will return a coro object - you can store this for future |
|
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96 | reference or ignore it, the thread itself will keep a reference to it's |
|
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97 | thread object - threads are alive on their 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: |
|
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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 | |
|
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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 $coro; |
|
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116 | |
|
|
117 | =item 2. Startup |
|
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118 | |
|
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119 | When a new coro thread is created, only a copy of the code reference |
|
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120 | and the arguments are stored, no extra memory for stacks and so on is |
|
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121 | allocated, keeping the coro thread in a low-memory state. |
|
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122 | |
|
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123 | Only when it actually starts executing will all the resources be finally |
|
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124 | allocated. |
|
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125 | |
|
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126 | The optional arguments specified at coro creation are available in C<@_>, |
|
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127 | similar to function calls. |
|
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128 | |
|
|
129 | =item 3. Running / Blocking |
|
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130 | |
|
|
131 | A lot can happen after the coro thread has started running. Quite usually, |
|
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132 | it will not run to the end in one go (because you could use a function |
|
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133 | instead), but it will give up the CPU regularly because it waits for |
|
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134 | external events. |
|
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135 | |
|
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136 | As long as a coro thread runs, it's coro object is available in the global |
|
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137 | variable C<$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 | |
|
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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 |
|
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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 | |
|
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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 | |
|
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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 |
|
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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 { |
|
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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"; |
|
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199 | }; |
|
|
200 | |
|
|
201 | And yet another way is to C<< ->cancel >> the coro thread from another |
|
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202 | thread: |
|
|
203 | |
|
|
204 | my $coro = async { |
|
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205 | exit 1; |
|
|
206 | }; |
|
|
207 | |
|
|
208 | $coro->cancel; # an also accept values for ->join to retrieve |
|
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209 | |
|
|
210 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
|
|
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 |
|
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214 | state. |
|
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215 | |
|
|
216 | So, cancelling a thread that runs in an XS event loop might not be the |
|
|
217 | best idea, but any other combination that deals with perl only (cancelling |
|
|
218 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
|
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219 | safe. |
|
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220 | |
|
|
221 | =item 5. Cleanup |
|
|
222 | |
|
|
223 | Threads will allocate various resources. Most but not all will be returned |
|
|
224 | when a thread terminates, during clean-up. |
|
|
225 | |
|
|
226 | Cleanup is quite similar to throwing an uncaught exception: perl will |
|
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227 | work it's way up through all subroutine calls and blocks. On it's way, it |
|
|
228 | will release all C<my> variables, undo all C<local>'s and free any other |
|
|
229 | resources truly local to the thread. |
|
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230 | |
|
|
231 | So, a common way to free resources is to keep them referenced only by my |
|
|
232 | variables: |
|
|
233 | |
|
|
234 | async { |
|
|
235 | my $big_cache = new Cache ...; |
|
|
236 | }; |
|
|
237 | |
|
|
238 | If there are no other references, then the C<$big_cache> object will be |
|
|
239 | freed when the thread terminates, regardless of how it does so. |
|
|
240 | |
|
|
241 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
|
|
242 | resources, but that's where the C<guard> methods come in handy: |
|
|
243 | |
|
|
244 | my $sem = new Coro::Semaphore; |
|
|
245 | |
|
|
246 | async { |
|
|
247 | my $lock_guard = $sem->guard; |
|
|
248 | # if we reutrn, or die or get cancelled, here, |
|
|
249 | # then the semaphore will be "up"ed. |
|
|
250 | }; |
|
|
251 | |
|
|
252 | The C<Guard::guard> function comes in handy for any custom cleanup you |
|
|
253 | might want to do: |
|
|
254 | |
|
|
255 | async { |
|
|
256 | my $window = new Gtk2::Window "toplevel"; |
|
|
257 | # The window will not be cleaned up automatically, even when $window |
|
|
258 | # gets freed, so use a guard to ensure it's destruction |
|
|
259 | # in case of an error: |
|
|
260 | my $window_guard = Guard::guard { $window->destroy }; |
|
|
261 | |
|
|
262 | # we are safe here |
|
|
263 | }; |
|
|
264 | |
|
|
265 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
|
|
266 | replacing the coro thread description: |
|
|
267 | |
|
|
268 | sub myfunction { |
|
|
269 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
|
|
270 | |
|
|
271 | # if we return or die here, the description will be restored |
|
|
272 | } |
|
|
273 | |
|
|
274 | =item 6. Viva La Zombie Muerte |
|
|
275 | |
|
|
276 | Even after a thread has terminated and cleaned up it's resources, the coro |
|
|
277 | object still is there and stores the return values of the thread. Only in |
|
|
278 | this state will the coro object be "reference counted" in the normal perl |
|
|
279 | sense: the thread code keeps a reference to it when it is active, but not |
|
|
280 | after it has terminated. |
|
|
281 | |
|
|
282 | The means the coro object gets freed automatically when the thread has |
|
|
283 | terminated and cleaned up and there arenot other references. |
|
|
284 | |
|
|
285 | If there are, the coro object will stay around, and you can call C<< |
|
|
286 | ->join >> as many times as you wish to retrieve the result values: |
|
|
287 | |
|
|
288 | async { |
|
|
289 | print "hi\n"; |
|
|
290 | 1 |
|
|
291 | }; |
|
|
292 | |
|
|
293 | # run the async above, and free everything before returning |
|
|
294 | # from Coro::cede: |
|
|
295 | Coro::cede; |
|
|
296 | |
|
|
297 | { |
|
|
298 | my $coro = async { |
|
|
299 | print "hi\n"; |
|
|
300 | 1 |
|
|
301 | }; |
|
|
302 | |
|
|
303 | # run the async above, and clean up, but do not free the coro |
|
|
304 | # object: |
|
|
305 | Coro::cede; |
|
|
306 | |
|
|
307 | # optionally retrieve the result values |
|
|
308 | my @results = $coro->join; |
|
|
309 | |
|
|
310 | # now $coro goes out of scope, and presumably gets freed |
|
|
311 | }; |
|
|
312 | |
|
|
313 | =back |
|
|
314 | |
68 | =cut |
315 | =cut |
69 | |
316 | |
70 | package Coro; |
317 | package Coro; |
71 | |
318 | |
72 | use strict qw(vars subs); |
319 | use common::sense; |
73 | no warnings "uninitialized"; |
320 | |
|
|
321 | use Carp (); |
74 | |
322 | |
75 | use Guard (); |
323 | use Guard (); |
76 | |
324 | |
77 | use Coro::State; |
325 | use Coro::State; |
78 | |
326 | |
… | |
… | |
80 | |
328 | |
81 | our $idle; # idle handler |
329 | our $idle; # idle handler |
82 | our $main; # main coro |
330 | our $main; # main coro |
83 | our $current; # current coro |
331 | our $current; # current coro |
84 | |
332 | |
85 | our $VERSION = 5.14; |
333 | our $VERSION = 5.371; |
86 | |
334 | |
87 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
335 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
88 | our %EXPORT_TAGS = ( |
336 | our %EXPORT_TAGS = ( |
89 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
337 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
90 | ); |
338 | ); |
91 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
339 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
92 | |
340 | |
… | |
… | |
123 | |
371 | |
124 | This variable is mainly useful to integrate Coro into event loops. It is |
372 | 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 |
373 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
126 | pretty low-level functionality. |
374 | pretty low-level functionality. |
127 | |
375 | |
128 | This variable stores either a Coro object or a callback. |
376 | This variable stores a Coro object that is put into the ready queue when |
|
|
377 | there are no other ready threads (without invoking any ready hooks). |
129 | |
378 | |
130 | If it is a callback, the it is called whenever the scheduler finds no |
379 | The default implementation dies with "FATAL: deadlock detected.", followed |
131 | ready coros to run. The default implementation prints "FATAL: |
380 | 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 | |
381 | |
139 | This hook is overwritten by modules such as C<Coro::EV> and |
382 | 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 |
383 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
141 | coro so the scheduler can run it. |
384 | coro so the scheduler can run it. |
142 | |
385 | |
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 |
386 | See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
150 | technique. |
|
|
151 | |
387 | |
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 | |
|
|
155 | =cut |
388 | =cut |
156 | |
389 | |
157 | $idle = sub { |
390 | # ||= because other modules could have provided their own by now |
158 | require Carp; |
391 | $idle ||= new Coro sub { |
159 | Carp::croak ("FATAL: deadlock detected"); |
392 | require Coro::Debug; |
|
|
393 | die "FATAL: deadlock detected.\n" |
|
|
394 | . Coro::Debug::ps_listing (); |
160 | }; |
395 | }; |
161 | |
396 | |
162 | # this coro is necessary because a coro |
397 | # this coro is necessary because a coro |
163 | # cannot destroy itself. |
398 | # cannot destroy itself. |
164 | our @destroy; |
399 | our @destroy; |
… | |
… | |
206 | Example: Create a new coro that just prints its arguments. |
441 | Example: Create a new coro that just prints its arguments. |
207 | |
442 | |
208 | async { |
443 | async { |
209 | print "@_\n"; |
444 | print "@_\n"; |
210 | } 1,2,3,4; |
445 | } 1,2,3,4; |
211 | |
|
|
212 | =cut |
|
|
213 | |
|
|
214 | sub async(&@) { |
|
|
215 | my $coro = new Coro @_; |
|
|
216 | $coro->ready; |
|
|
217 | $coro |
|
|
218 | } |
|
|
219 | |
446 | |
220 | =item async_pool { ... } [@args...] |
447 | =item async_pool { ... } [@args...] |
221 | |
448 | |
222 | Similar to C<async>, but uses a coro pool, so you should not call |
449 | Similar to C<async>, but uses a coro pool, so you should not call |
223 | terminate or join on it (although you are allowed to), and you get a |
450 | terminate or join on it (although you are allowed to), and you get a |
… | |
… | |
280 | =item schedule |
507 | =item schedule |
281 | |
508 | |
282 | Calls the scheduler. The scheduler will find the next coro that is |
509 | Calls the scheduler. The scheduler will find the next coro that is |
283 | to be run from the ready queue and switches to it. The next coro |
510 | to be run from the ready queue and switches to it. The next coro |
284 | to be run is simply the one with the highest priority that is longest |
511 | to be run is simply the one with the highest priority that is longest |
285 | in its ready queue. If there is no coro ready, it will clal the |
512 | in its ready queue. If there is no coro ready, it will call the |
286 | C<$Coro::idle> hook. |
513 | C<$Coro::idle> hook. |
287 | |
514 | |
288 | Please note that the current coro will I<not> be put into the ready |
515 | Please note that the current coro will I<not> be put into the ready |
289 | queue, so calling this function usually means you will never be called |
516 | queue, so calling this function usually means you will never be called |
290 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
517 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
… | |
… | |
587 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
814 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
588 | } |
815 | } |
589 | |
816 | |
590 | =item $coro->on_destroy (\&cb) |
817 | =item $coro->on_destroy (\&cb) |
591 | |
818 | |
592 | Registers a callback that is called when this coro gets destroyed, |
819 | Registers a callback that is called when this coro thread gets destroyed, |
593 | but before it is joined. The callback gets passed the terminate arguments, |
820 | but before it is joined. The callback gets passed the terminate arguments, |
594 | if any, and I<must not> die, under any circumstances. |
821 | if any, and I<must not> die, under any circumstances. |
595 | |
822 | |
|
|
823 | There can be any number of C<on_destroy> callbacks per coro. |
|
|
824 | |
596 | =cut |
825 | =cut |
597 | |
826 | |
598 | sub on_destroy { |
827 | sub on_destroy { |
599 | my ($self, $cb) = @_; |
828 | my ($self, $cb) = @_; |
600 | |
829 | |
… | |
… | |
602 | } |
831 | } |
603 | |
832 | |
604 | =item $oldprio = $coro->prio ($newprio) |
833 | =item $oldprio = $coro->prio ($newprio) |
605 | |
834 | |
606 | Sets (or gets, if the argument is missing) the priority of the |
835 | Sets (or gets, if the argument is missing) the priority of the |
607 | coro. Higher priority coro get run before lower priority |
836 | coro thread. Higher priority coro get run before lower priority |
608 | coro. Priorities are small signed integers (currently -4 .. +3), |
837 | coros. Priorities are small signed integers (currently -4 .. +3), |
609 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
838 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
610 | to get then): |
839 | to get then): |
611 | |
840 | |
612 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
841 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
613 | 3 > 1 > 0 > -1 > -3 > -4 |
842 | 3 > 1 > 0 > -1 > -3 > -4 |
614 | |
843 | |
615 | # set priority to HIGH |
844 | # set priority to HIGH |
616 | current->prio (PRIO_HIGH); |
845 | current->prio (PRIO_HIGH); |
617 | |
846 | |
618 | The idle coro ($Coro::idle) always has a lower priority than any |
847 | The idle coro thread ($Coro::idle) always has a lower priority than any |
619 | existing coro. |
848 | existing coro. |
620 | |
849 | |
621 | Changing the priority of the current coro will take effect immediately, |
850 | Changing the priority of the current coro will take effect immediately, |
622 | but changing the priority of coro in the ready queue (but not |
851 | but changing the priority of a coro in the ready queue (but not running) |
623 | running) will only take effect after the next schedule (of that |
852 | will only take effect after the next schedule (of that coro). This is a |
624 | coro). This is a bug that will be fixed in some future version. |
853 | bug that will be fixed in some future version. |
625 | |
854 | |
626 | =item $newprio = $coro->nice ($change) |
855 | =item $newprio = $coro->nice ($change) |
627 | |
856 | |
628 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
857 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
629 | higher values mean lower priority, just as in unix). |
858 | higher values mean lower priority, just as in UNIX's nice command). |
630 | |
859 | |
631 | =item $olddesc = $coro->desc ($newdesc) |
860 | =item $olddesc = $coro->desc ($newdesc) |
632 | |
861 | |
633 | Sets (or gets in case the argument is missing) the description for this |
862 | Sets (or gets in case the argument is missing) the description for this |
634 | coro. This is just a free-form string you can associate with a |
863 | coro thread. This is just a free-form string you can associate with a |
635 | coro. |
864 | coro. |
636 | |
865 | |
637 | This method simply sets the C<< $coro->{desc} >> member to the given |
866 | This method simply sets the C<< $coro->{desc} >> member to the given |
638 | string. You can modify this member directly if you wish. |
867 | string. You can modify this member directly if you wish, and in fact, this |
|
|
868 | is often preferred to indicate major processing states that cna then be |
|
|
869 | seen for example in a L<Coro::Debug> session: |
|
|
870 | |
|
|
871 | sub my_long_function { |
|
|
872 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
873 | ... |
|
|
874 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
875 | ... |
|
|
876 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
877 | ... |
|
|
878 | } |
639 | |
879 | |
640 | =cut |
880 | =cut |
641 | |
881 | |
642 | sub desc { |
882 | sub desc { |
643 | my $old = $_[0]{desc}; |
883 | my $old = $_[0]{desc}; |
… | |
… | |
680 | returning a new coderef. Unblocking means that calling the new coderef |
920 | returning a new coderef. Unblocking means that calling the new coderef |
681 | will return immediately without blocking, returning nothing, while the |
921 | will return immediately without blocking, returning nothing, while the |
682 | original code ref will be called (with parameters) from within another |
922 | original code ref will be called (with parameters) from within another |
683 | coro. |
923 | coro. |
684 | |
924 | |
685 | The reason this function exists is that many event libraries (such as the |
925 | The reason this function exists is that many event libraries (such as |
686 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
926 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
687 | of reentrancy). This means you must not block within event callbacks, |
927 | of reentrancy). This means you must not block within event callbacks, |
688 | otherwise you might suffer from crashes or worse. The only event library |
928 | otherwise you might suffer from crashes or worse. The only event library |
689 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
929 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
930 | you might still run into deadlocks if all event loops are blocked). |
|
|
931 | |
|
|
932 | Coro will try to catch you when you block in the event loop |
|
|
933 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
934 | only works when you do not run your own event loop. |
690 | |
935 | |
691 | This function allows your callbacks to block by executing them in another |
936 | This function allows your callbacks to block by executing them in another |
692 | coro where it is safe to block. One example where blocking is handy |
937 | coro where it is safe to block. One example where blocking is handy |
693 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
938 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
694 | disk, for example. |
939 | disk, for example. |
… | |
… | |
736 | unshift @unblock_queue, [$cb, @_]; |
981 | unshift @unblock_queue, [$cb, @_]; |
737 | $unblock_scheduler->ready; |
982 | $unblock_scheduler->ready; |
738 | } |
983 | } |
739 | } |
984 | } |
740 | |
985 | |
741 | =item $cb = Coro::rouse_cb |
986 | =item $cb = rouse_cb |
742 | |
987 | |
743 | Create and return a "rouse callback". That's a code reference that, |
988 | Create and return a "rouse callback". That's a code reference that, |
744 | when called, will remember a copy of its arguments and notify the owner |
989 | when called, will remember a copy of its arguments and notify the owner |
745 | coro of the callback. |
990 | coro of the callback. |
746 | |
991 | |
747 | See the next function. |
992 | See the next function. |
748 | |
993 | |
749 | =item @args = Coro::rouse_wait [$cb] |
994 | =item @args = rouse_wait [$cb] |
750 | |
995 | |
751 | Wait for the specified rouse callback (or the last one that was created in |
996 | Wait for the specified rouse callback (or the last one that was created in |
752 | this coro). |
997 | this coro). |
753 | |
998 | |
754 | As soon as the callback is invoked (or when the callback was invoked |
999 | As soon as the callback is invoked (or when the callback was invoked |
755 | before C<rouse_wait>), it will return the arguments originally passed to |
1000 | before C<rouse_wait>), it will return the arguments originally passed to |
756 | the rouse callback. |
1001 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
1002 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
1003 | statement at the end. |
757 | |
1004 | |
758 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
1005 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
759 | |
1006 | |
760 | =back |
1007 | =back |
761 | |
1008 | |
762 | =cut |
1009 | =cut |
|
|
1010 | |
|
|
1011 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1012 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1013 | |
|
|
1014 | *{"Coro::$module\::new"} = sub { |
|
|
1015 | require "Coro/$module.pm"; |
|
|
1016 | |
|
|
1017 | # some modules have their new predefined in State.xs, some don't |
|
|
1018 | *{"Coro::$module\::new"} = $old |
|
|
1019 | if $old; |
|
|
1020 | |
|
|
1021 | goto &{"Coro::$module\::new"}; |
|
|
1022 | }; |
|
|
1023 | } |
763 | |
1024 | |
764 | 1; |
1025 | 1; |
765 | |
1026 | |
766 | =head1 HOW TO WAIT FOR A CALLBACK |
1027 | =head1 HOW TO WAIT FOR A CALLBACK |
767 | |
1028 | |
… | |
… | |
849 | the windows process emulation enabled under unix roughly halves perl |
1110 | the windows process emulation enabled under unix roughly halves perl |
850 | performance, even when not used. |
1111 | performance, even when not used. |
851 | |
1112 | |
852 | =item coro switching is not signal safe |
1113 | =item coro switching is not signal safe |
853 | |
1114 | |
854 | You must not switch to another coro from within a signal handler |
1115 | You must not switch to another coro from within a signal handler (only |
855 | (only relevant with %SIG - most event libraries provide safe signals). |
1116 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1117 | you are sure you are not interrupting a Coro function. |
856 | |
1118 | |
857 | That means you I<MUST NOT> call any function that might "block" the |
1119 | That means you I<MUST NOT> call any function that might "block" the |
858 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1120 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
859 | anything that calls those. Everything else, including calling C<ready>, |
1121 | anything that calls those. Everything else, including calling C<ready>, |
860 | works. |
1122 | works. |
861 | |
1123 | |
862 | =back |
1124 | =back |
863 | |
1125 | |
864 | |
1126 | |
|
|
1127 | =head1 WINDOWS PROCESS EMULATION |
|
|
1128 | |
|
|
1129 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1130 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1131 | while in the same mail making rather confused statements about perl |
|
|
1132 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1133 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1134 | it is probably not obvious to everybody). |
|
|
1135 | |
|
|
1136 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1137 | scripting languages given on the perl workshop 2009: |
|
|
1138 | |
|
|
1139 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1140 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1141 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1142 | |
|
|
1143 | It does that by using threads instead of OS processes. The difference |
|
|
1144 | between processes and threads is that threads share memory (and other |
|
|
1145 | state, such as files) between threads within a single process, while |
|
|
1146 | processes do not share anything (at least not semantically). That |
|
|
1147 | means that modifications done by one thread are seen by others, while |
|
|
1148 | modifications by one process are not seen by other processes. |
|
|
1149 | |
|
|
1150 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1151 | process, all state is copied (memory is copied physically, files and code |
|
|
1152 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1153 | the same behaviour can be achieved by using operating system processes, |
|
|
1154 | except that UNIX typically uses hardware built into the system to do this |
|
|
1155 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1156 | software (rather efficiently, but of course it is still much slower than |
|
|
1157 | dedicated hardware). |
|
|
1158 | |
|
|
1159 | As mentioned before, loading code, modifying code, modifying data |
|
|
1160 | structures and so on is only visible in the ithreads process doing the |
|
|
1161 | modification, not in other ithread processes within the same OS process. |
|
|
1162 | |
|
|
1163 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1164 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1165 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1166 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1167 | faster). |
|
|
1168 | |
|
|
1169 | Sharing data is in the i-threads model is done by transfering data |
|
|
1170 | structures between threads using copying semantics, which is very slow - |
|
|
1171 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1172 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1173 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1174 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1175 | real threads, refer to my talk for details). |
|
|
1176 | |
|
|
1177 | As summary, i-threads *use* threads to implement processes, while |
|
|
1178 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1179 | processes. I-threads slow down every perl program when enabled, and |
|
|
1180 | outside of windows, serve no (or little) practical purpose, but |
|
|
1181 | disadvantages every single-threaded Perl program. |
|
|
1182 | |
|
|
1183 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1184 | misleading as it implies that it implements some kind of thread model for |
|
|
1185 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1186 | actual use and behaviour of it much better. |
|
|
1187 | |
865 | =head1 SEE ALSO |
1188 | =head1 SEE ALSO |
866 | |
1189 | |
867 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1190 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
868 | |
1191 | |
869 | Debugging: L<Coro::Debug>. |
1192 | Debugging: L<Coro::Debug>. |