… | |
… | |
16 | cede; # yield to coro |
16 | cede; # yield to coro |
17 | print "3\n"; |
17 | print "3\n"; |
18 | cede; # and again |
18 | cede; # and again |
19 | |
19 | |
20 | # use locking |
20 | # use locking |
21 | use Coro::Semaphore; |
|
|
22 | my $lock = new Coro::Semaphore; |
21 | my $lock = new Coro::Semaphore; |
23 | my $locked; |
22 | my $locked; |
24 | |
23 | |
25 | $lock->down; |
24 | $lock->down; |
26 | $locked = 1; |
25 | $locked = 1; |
… | |
… | |
40 | points in your program, so locking and parallel access are rarely an |
39 | points in your program, so locking and parallel access are rarely an |
41 | issue, making thread programming much safer and easier than using other |
40 | issue, making thread programming much safer and easier than using other |
42 | thread models. |
41 | thread models. |
43 | |
42 | |
44 | Unlike the so-called "Perl threads" (which are not actually real threads |
43 | 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 |
44 | but only the windows process emulation (see section of same name for |
46 | as processes), Coro provides a full shared address space, which makes |
45 | more details) ported to UNIX, and as such act as processes), Coro |
47 | communication between threads very easy. And Coro's threads are fast, |
46 | provides a full shared address space, which makes communication between |
48 | too: disabling the Windows process emulation code in your perl and using |
47 | 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 |
48 | process emulation code in your perl and using Coro can easily result in |
50 | programs. A parallel matrix multiplication benchmark runs over 300 times |
49 | a two to four times speed increase for your programs. A parallel matrix |
|
|
50 | multiplication benchmark (very communication-intensive) runs over 300 |
51 | faster on a single core than perl's pseudo-threads on a quad core using |
51 | times faster on a single core than perls pseudo-threads on a quad core |
52 | all four cores. |
52 | using all four cores. |
53 | |
53 | |
54 | Coro achieves that by supporting multiple running interpreters that share |
54 | Coro achieves that by supporting multiple running interpreters that share |
55 | data, which is especially useful to code pseudo-parallel processes and |
55 | data, which is especially useful to code pseudo-parallel processes and |
56 | for event-based programming, such as multiple HTTP-GET requests running |
56 | 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 |
57 | 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). |
63 | variables (see L<Coro::State> for more configuration and background info). |
64 | |
64 | |
65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
66 | module family is quite large. |
66 | module family is quite large. |
67 | |
67 | |
|
|
68 | =head1 CORO THREAD LIFE CYCLE |
|
|
69 | |
|
|
70 | During the long and exciting (or not) life of a coro thread, it goes |
|
|
71 | through a number of states: |
|
|
72 | |
|
|
73 | =over 4 |
|
|
74 | |
|
|
75 | =item 1. Creation |
|
|
76 | |
|
|
77 | The first thing in the life of a coro thread is it's creation - |
|
|
78 | obviously. The typical way to create a thread is to call the C<async |
|
|
79 | BLOCK> function: |
|
|
80 | |
|
|
81 | async { |
|
|
82 | # thread code goes here |
|
|
83 | }; |
|
|
84 | |
|
|
85 | You can also pass arguments, which are put in C<@_>: |
|
|
86 | |
|
|
87 | async { |
|
|
88 | print $_[1]; # prints 2 |
|
|
89 | } 1, 2, 3; |
|
|
90 | |
|
|
91 | This creates a new coro thread and puts it into the ready queue, meaning |
|
|
92 | it will run as soon as the CPU is free for it. |
|
|
93 | |
|
|
94 | C<async> will return a Coro object - you can store this for future |
|
|
95 | reference or ignore it - a thread that is running, ready to run or waiting |
|
|
96 | for some event is alive on it's own. |
|
|
97 | |
|
|
98 | Another way to create a thread is to call the C<new> constructor with a |
|
|
99 | code-reference: |
|
|
100 | |
|
|
101 | new Coro sub { |
|
|
102 | # thread code goes here |
|
|
103 | }, @optional_arguments; |
|
|
104 | |
|
|
105 | This is quite similar to calling C<async>, but the important difference is |
|
|
106 | that the new thread is not put into the ready queue, so the thread will |
|
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107 | not run until somebody puts it there. C<async> is, therefore, identical to |
|
|
108 | this sequence: |
|
|
109 | |
|
|
110 | my $coro = new Coro sub { |
|
|
111 | # thread code goes here |
|
|
112 | }; |
|
|
113 | $coro->ready; |
|
|
114 | return $coro; |
|
|
115 | |
|
|
116 | =item 2. Startup |
|
|
117 | |
|
|
118 | When a new coro thread is created, only a copy of the code reference |
|
|
119 | and the arguments are stored, no extra memory for stacks and so on is |
|
|
120 | allocated, keeping the coro thread in a low-memory state. |
|
|
121 | |
|
|
122 | Only when it actually starts executing will all the resources be finally |
|
|
123 | allocated. |
|
|
124 | |
|
|
125 | The optional arguments specified at coro creation are available in C<@_>, |
|
|
126 | similar to function calls. |
|
|
127 | |
|
|
128 | =item 3. Running / Blocking |
|
|
129 | |
|
|
130 | A lot can happen after the coro thread has started running. Quite usually, |
|
|
131 | it will not run to the end in one go (because you could use a function |
|
|
132 | instead), but it will give up the CPU regularly because it waits for |
|
|
133 | external events. |
|
|
134 | |
|
|
135 | As long as a coro thread runs, its Coro object is available in the global |
|
|
136 | variable C<$Coro::current>. |
|
|
137 | |
|
|
138 | The low-level way to give up the CPU is to call the scheduler, which |
|
|
139 | selects a new coro thread to run: |
|
|
140 | |
|
|
141 | Coro::schedule; |
|
|
142 | |
|
|
143 | Since running threads are not in the ready queue, calling the scheduler |
|
|
144 | without doing anything else will block the coro thread forever - you need |
|
|
145 | to arrange either for the coro to put woken up (readied) by some other |
|
|
146 | event or some other thread, or you can put it into the ready queue before |
|
|
147 | scheduling: |
|
|
148 | |
|
|
149 | # this is exactly what Coro::cede does |
|
|
150 | $Coro::current->ready; |
|
|
151 | Coro::schedule; |
|
|
152 | |
|
|
153 | All the higher-level synchronisation methods (Coro::Semaphore, |
|
|
154 | Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<< |
|
|
155 | Coro::schedule >>. |
|
|
156 | |
|
|
157 | While the coro thread is running it also might get assigned a C-level |
|
|
158 | thread, or the C-level thread might be unassigned from it, as the Coro |
|
|
159 | runtime wishes. A C-level thread needs to be assigned when your perl |
|
|
160 | thread calls into some C-level function and that function in turn calls |
|
|
161 | perl and perl then wants to switch coroutines. This happens most often |
|
|
162 | when you run an event loop and block in the callback, or when perl |
|
|
163 | itself calls some function such as C<AUTOLOAD> or methods via the C<tie> |
|
|
164 | mechanism. |
|
|
165 | |
|
|
166 | =item 4. Termination |
|
|
167 | |
|
|
168 | Many threads actually terminate after some time. There are a number of |
|
|
169 | ways to terminate a coro thread, the simplest is returning from the |
|
|
170 | top-level code reference: |
|
|
171 | |
|
|
172 | async { |
|
|
173 | # after returning from here, the coro thread is terminated |
|
|
174 | }; |
|
|
175 | |
|
|
176 | async { |
|
|
177 | return if 0.5 < rand; # terminate a little earlier, maybe |
|
|
178 | print "got a chance to print this\n"; |
|
|
179 | # or here |
|
|
180 | }; |
|
|
181 | |
|
|
182 | Any values returned from the coroutine can be recovered using C<< ->join |
|
|
183 | >>: |
|
|
184 | |
|
|
185 | my $coro = async { |
|
|
186 | "hello, world\n" # return a string |
|
|
187 | }; |
|
|
188 | |
|
|
189 | my $hello_world = $coro->join; |
|
|
190 | |
|
|
191 | print $hello_world; |
|
|
192 | |
|
|
193 | Another way to terminate is to call C<< Coro::terminate >>, which at any |
|
|
194 | subroutine call nesting level: |
|
|
195 | |
|
|
196 | async { |
|
|
197 | Coro::terminate "return value 1", "return value 2"; |
|
|
198 | }; |
|
|
199 | |
|
|
200 | Yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the coro |
|
|
201 | thread from another thread: |
|
|
202 | |
|
|
203 | my $coro = async { |
|
|
204 | exit 1; |
|
|
205 | }; |
|
|
206 | |
|
|
207 | $coro->cancel; # also accepts values for ->join to retrieve |
|
|
208 | |
|
|
209 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
|
|
210 | actually exiting, and might leave C libraries and XS modules in a weird |
|
|
211 | state. Unlike other thread implementations, however, Coro is exceptionally |
|
|
212 | safe with regards to cancellation, as perl will always be in a consistent |
|
|
213 | state, and for those cases where you want to do truly marvellous things |
|
|
214 | with your coro while it is being cancelled - that is, make sure all |
|
|
215 | cleanup code is executed from the thread being cancelled - there is even a |
|
|
216 | C<< ->safe_cancel >> method. |
|
|
217 | |
|
|
218 | So, cancelling a thread that runs in an XS event loop might not be the |
|
|
219 | best idea, but any other combination that deals with perl only (cancelling |
|
|
220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
|
|
221 | safe. |
|
|
222 | |
|
|
223 | Last not least, a coro thread object that isn't referenced is C<< |
|
|
224 | ->cancel >>'ed automatically - just like other objects in Perl. This |
|
|
225 | is not such a common case, however - a running thread is referencedy by |
|
|
226 | C<$Coro::current>, a thread ready to run is referenced by the ready queue, |
|
|
227 | a thread waiting on a lock or semaphore is referenced by being in some |
|
|
228 | wait list and so on. But a thread that isn't in any of those queues gets |
|
|
229 | cancelled: |
|
|
230 | |
|
|
231 | async { |
|
|
232 | schedule; # cede to other coros, don't go into the ready queue |
|
|
233 | }; |
|
|
234 | |
|
|
235 | cede; |
|
|
236 | # now the async above is destroyed, as it is not referenced by anything. |
|
|
237 | |
|
|
238 | A slightly embellished example might make it clearer: |
|
|
239 | |
|
|
240 | async { |
|
|
241 | my $guard = Guard::guard { print "destroyed\n" }; |
|
|
242 | schedule while 1; |
|
|
243 | }; |
|
|
244 | |
|
|
245 | cede; |
|
|
246 | |
|
|
247 | Superficially one might not expect any output - since the C<async> |
|
|
248 | implements an endless loop, the C<$guard> will not be cleaned up. However, |
|
|
249 | since the thread object returned by C<async> is not stored anywhere, the |
|
|
250 | thread is initially referenced because it is in the ready queue, when it |
|
|
251 | runs it is referenced by C<$Coro::current>, but when it calls C<schedule>, |
|
|
252 | it gets C<cancel>ed causing the guard object to be destroyed (see the next |
|
|
253 | section), and printing it's message. |
|
|
254 | |
|
|
255 | If this seems a bit drastic, remember that this only happens when nothing |
|
|
256 | references the thread anymore, which means there is no way to further |
|
|
257 | execute it, ever. The only options at this point are leaking the thread, |
|
|
258 | or cleaning it up, which brings us to... |
|
|
259 | |
|
|
260 | =item 5. Cleanup |
|
|
261 | |
|
|
262 | Threads will allocate various resources. Most but not all will be returned |
|
|
263 | when a thread terminates, during clean-up. |
|
|
264 | |
|
|
265 | Cleanup is quite similar to throwing an uncaught exception: perl will |
|
|
266 | work it's way up through all subroutine calls and blocks. On it's way, it |
|
|
267 | will release all C<my> variables, undo all C<local>'s and free any other |
|
|
268 | resources truly local to the thread. |
|
|
269 | |
|
|
270 | So, a common way to free resources is to keep them referenced only by my |
|
|
271 | variables: |
|
|
272 | |
|
|
273 | async { |
|
|
274 | my $big_cache = new Cache ...; |
|
|
275 | }; |
|
|
276 | |
|
|
277 | If there are no other references, then the C<$big_cache> object will be |
|
|
278 | freed when the thread terminates, regardless of how it does so. |
|
|
279 | |
|
|
280 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
|
|
281 | resources, but that's where the C<guard> methods come in handy: |
|
|
282 | |
|
|
283 | my $sem = new Coro::Semaphore; |
|
|
284 | |
|
|
285 | async { |
|
|
286 | my $lock_guard = $sem->guard; |
|
|
287 | # if we return, or die or get cancelled, here, |
|
|
288 | # then the semaphore will be "up"ed. |
|
|
289 | }; |
|
|
290 | |
|
|
291 | The C<Guard::guard> function comes in handy for any custom cleanup you |
|
|
292 | might want to do (but you cannot switch to other coroutines from those |
|
|
293 | code blocks): |
|
|
294 | |
|
|
295 | async { |
|
|
296 | my $window = new Gtk2::Window "toplevel"; |
|
|
297 | # The window will not be cleaned up automatically, even when $window |
|
|
298 | # gets freed, so use a guard to ensure it's destruction |
|
|
299 | # in case of an error: |
|
|
300 | my $window_guard = Guard::guard { $window->destroy }; |
|
|
301 | |
|
|
302 | # we are safe here |
|
|
303 | }; |
|
|
304 | |
|
|
305 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
|
|
306 | replacing the coro thread description: |
|
|
307 | |
|
|
308 | sub myfunction { |
|
|
309 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
|
|
310 | |
|
|
311 | # if we return or die here, the description will be restored |
|
|
312 | } |
|
|
313 | |
|
|
314 | =item 6. Viva La Zombie Muerte |
|
|
315 | |
|
|
316 | Even after a thread has terminated and cleaned up its resources, the Coro |
|
|
317 | object still is there and stores the return values of the thread. |
|
|
318 | |
|
|
319 | When there are no other references, it will simply be cleaned up and |
|
|
320 | freed. |
|
|
321 | |
|
|
322 | If there areany references, the Coro object will stay around, and you |
|
|
323 | can call C<< ->join >> as many times as you wish to retrieve the result |
|
|
324 | values: |
|
|
325 | |
|
|
326 | async { |
|
|
327 | print "hi\n"; |
|
|
328 | 1 |
|
|
329 | }; |
|
|
330 | |
|
|
331 | # run the async above, and free everything before returning |
|
|
332 | # from Coro::cede: |
|
|
333 | Coro::cede; |
|
|
334 | |
|
|
335 | { |
|
|
336 | my $coro = async { |
|
|
337 | print "hi\n"; |
|
|
338 | 1 |
|
|
339 | }; |
|
|
340 | |
|
|
341 | # run the async above, and clean up, but do not free the coro |
|
|
342 | # object: |
|
|
343 | Coro::cede; |
|
|
344 | |
|
|
345 | # optionally retrieve the result values |
|
|
346 | my @results = $coro->join; |
|
|
347 | |
|
|
348 | # now $coro goes out of scope, and presumably gets freed |
|
|
349 | }; |
|
|
350 | |
|
|
351 | =back |
|
|
352 | |
68 | =cut |
353 | =cut |
69 | |
354 | |
70 | package Coro; |
355 | package Coro; |
71 | |
356 | |
72 | use strict qw(vars subs); |
357 | use common::sense; |
73 | no warnings "uninitialized"; |
358 | |
|
|
359 | use Carp (); |
74 | |
360 | |
75 | use Guard (); |
361 | use Guard (); |
76 | |
362 | |
77 | use Coro::State; |
363 | use Coro::State; |
78 | |
364 | |
… | |
… | |
80 | |
366 | |
81 | our $idle; # idle handler |
367 | our $idle; # idle handler |
82 | our $main; # main coro |
368 | our $main; # main coro |
83 | our $current; # current coro |
369 | our $current; # current coro |
84 | |
370 | |
85 | our $VERSION = 5.151; |
371 | our $VERSION = 6.23; |
86 | |
372 | |
87 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
373 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
88 | our %EXPORT_TAGS = ( |
374 | our %EXPORT_TAGS = ( |
89 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
375 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
90 | ); |
376 | ); |
91 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
377 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
92 | |
378 | |
… | |
… | |
95 | =over 4 |
381 | =over 4 |
96 | |
382 | |
97 | =item $Coro::main |
383 | =item $Coro::main |
98 | |
384 | |
99 | This variable stores the Coro object that represents the main |
385 | This variable stores the Coro object that represents the main |
100 | program. While you cna C<ready> it and do most other things you can do to |
386 | program. While you can C<ready> it and do most other things you can do to |
101 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
387 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
102 | whether you are running in the main program or not. |
388 | whether you are running in the main program or not. |
103 | |
389 | |
104 | =cut |
390 | =cut |
105 | |
391 | |
… | |
… | |
123 | |
409 | |
124 | This variable is mainly useful to integrate Coro into event loops. It is |
410 | 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 |
411 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
126 | pretty low-level functionality. |
412 | pretty low-level functionality. |
127 | |
413 | |
128 | This variable stores either a Coro object or a callback. |
414 | This variable stores a Coro object that is put into the ready queue when |
|
|
415 | there are no other ready threads (without invoking any ready hooks). |
129 | |
416 | |
130 | If it is a callback, the it is called whenever the scheduler finds no |
417 | The default implementation dies with "FATAL: deadlock detected.", followed |
131 | ready coros to run. The default implementation prints "FATAL: |
418 | 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 | |
419 | |
139 | This hook is overwritten by modules such as C<Coro::EV> and |
420 | 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 |
421 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
141 | coro so the scheduler can run it. |
422 | coro so the scheduler can run it. |
142 | |
423 | |
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 |
424 | 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 | |
425 | |
155 | =cut |
426 | =cut |
156 | |
427 | |
157 | $idle = sub { |
428 | # ||= because other modules could have provided their own by now |
158 | require Carp; |
429 | $idle ||= new Coro sub { |
159 | Carp::croak ("FATAL: deadlock detected"); |
430 | require Coro::Debug; |
|
|
431 | die "FATAL: deadlock detected.\n" |
|
|
432 | . Coro::Debug::ps_listing (); |
160 | }; |
433 | }; |
161 | |
434 | |
162 | # this coro is necessary because a coro |
435 | # this coro is necessary because a coro |
163 | # cannot destroy itself. |
436 | # cannot destroy itself. |
164 | our @destroy; |
437 | our @destroy; |
165 | our $manager; |
438 | our $manager; |
166 | |
439 | |
167 | $manager = new Coro sub { |
440 | $manager = new Coro sub { |
168 | while () { |
441 | while () { |
169 | Coro::State::cancel shift @destroy |
442 | _destroy shift @destroy |
170 | while @destroy; |
443 | while @destroy; |
171 | |
444 | |
172 | &schedule; |
445 | &schedule; |
173 | } |
446 | } |
174 | }; |
447 | }; |
… | |
… | |
206 | Example: Create a new coro that just prints its arguments. |
479 | Example: Create a new coro that just prints its arguments. |
207 | |
480 | |
208 | async { |
481 | async { |
209 | print "@_\n"; |
482 | print "@_\n"; |
210 | } 1,2,3,4; |
483 | } 1,2,3,4; |
211 | |
|
|
212 | =cut |
|
|
213 | |
|
|
214 | sub async(&@) { |
|
|
215 | my $coro = new Coro @_; |
|
|
216 | $coro->ready; |
|
|
217 | $coro |
|
|
218 | } |
|
|
219 | |
484 | |
220 | =item async_pool { ... } [@args...] |
485 | =item async_pool { ... } [@args...] |
221 | |
486 | |
222 | Similar to C<async>, but uses a coro pool, so you should not call |
487 | Similar to C<async>, but uses a coro pool, so you should not call |
223 | terminate or join on it (although you are allowed to), and you get a |
488 | terminate or join on it (although you are allowed to), and you get a |
… | |
… | |
280 | =item schedule |
545 | =item schedule |
281 | |
546 | |
282 | Calls the scheduler. The scheduler will find the next coro that is |
547 | Calls the scheduler. The scheduler will find the next coro that is |
283 | to be run from the ready queue and switches to it. The next coro |
548 | to be run from the ready queue and switches to it. The next coro |
284 | to be run is simply the one with the highest priority that is longest |
549 | to be run is simply the one with the highest priority that is longest |
285 | in its ready queue. If there is no coro ready, it will clal the |
550 | in its ready queue. If there is no coro ready, it will call the |
286 | C<$Coro::idle> hook. |
551 | C<$Coro::idle> hook. |
287 | |
552 | |
288 | Please note that the current coro will I<not> be put into the ready |
553 | 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 |
554 | 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 >>, |
555 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
… | |
… | |
316 | coro, regardless of priority. This is useful sometimes to ensure |
581 | coro, regardless of priority. This is useful sometimes to ensure |
317 | progress is made. |
582 | progress is made. |
318 | |
583 | |
319 | =item terminate [arg...] |
584 | =item terminate [arg...] |
320 | |
585 | |
321 | Terminates the current coro with the given status values (see L<cancel>). |
586 | Terminates the current coro with the given status values (see |
|
|
587 | L<cancel>). The values will not be copied, but referenced directly. |
322 | |
588 | |
323 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
589 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
324 | |
590 | |
325 | These function install enter and leave winders in the current scope. The |
591 | These function install enter and leave winders in the current scope. The |
326 | enter block will be executed when on_enter is called and whenever the |
592 | enter block will be executed when on_enter is called and whenever the |
… | |
… | |
482 | To avoid this, it is best to put a suspended coro into the ready queue |
748 | To avoid this, it is best to put a suspended coro into the ready queue |
483 | unconditionally, as every synchronisation mechanism must protect itself |
749 | unconditionally, as every synchronisation mechanism must protect itself |
484 | against spurious wakeups, and the one in the Coro family certainly do |
750 | against spurious wakeups, and the one in the Coro family certainly do |
485 | that. |
751 | that. |
486 | |
752 | |
|
|
753 | =item $state->is_new |
|
|
754 | |
|
|
755 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
756 | yet. Those states basically consist of only the code reference to call and |
|
|
757 | the arguments, but consumes very little other resources. New states will |
|
|
758 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
759 | |
|
|
760 | =item $state->is_zombie |
|
|
761 | |
|
|
762 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
763 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
764 | C<safe_cancel>'ed or simply went out of scope. |
|
|
765 | |
|
|
766 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
767 | exited and only stores and exit status and no other resources is called a |
|
|
768 | "zombie". |
|
|
769 | |
487 | =item $is_ready = $coro->is_ready |
770 | =item $is_ready = $coro->is_ready |
488 | |
771 | |
489 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
772 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
490 | object gets destroyed, it will eventually be scheduled by the scheduler. |
773 | object gets destroyed, it will eventually be scheduled by the scheduler. |
491 | |
774 | |
… | |
… | |
500 | Returns true iff this Coro object has been suspended. Suspended Coros will |
783 | Returns true iff this Coro object has been suspended. Suspended Coros will |
501 | not ever be scheduled. |
784 | not ever be scheduled. |
502 | |
785 | |
503 | =item $coro->cancel (arg...) |
786 | =item $coro->cancel (arg...) |
504 | |
787 | |
505 | Terminates the given Coro and makes it return the given arguments as |
788 | Terminates the given Coro thread and makes it return the given arguments as |
506 | status (default: the empty list). Never returns if the Coro is the |
789 | status (default: an empty list). Never returns if the Coro is the |
507 | current Coro. |
790 | current Coro. |
508 | |
791 | |
509 | =cut |
792 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
793 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
794 | bad things can happen, or if the cancelled thread insists on running |
|
|
795 | complicated cleanup handlers that rely on its thread context, things will |
|
|
796 | not work. |
510 | |
797 | |
511 | sub cancel { |
798 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
512 | my $self = shift; |
799 | a thread context, and is not allowed to switch to other threads. On the |
|
|
800 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
801 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
802 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
803 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
513 | |
804 | |
514 | if ($current == $self) { |
805 | The arguments to C<< ->cancel >> are not copied, but instead will |
515 | terminate @_; |
806 | be referenced directly (e.g. if you pass C<$var> and after the call |
516 | } else { |
807 | change that variable, then you might change the return values passed to |
517 | $self->{_status} = [@_]; |
808 | e.g. C<join>, so don't do that). |
518 | Coro::State::cancel $self; |
809 | |
|
|
810 | The resources of the Coro are usually freed (or destructed) before this |
|
|
811 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
812 | in some cases the manager thread has to run first to actually destruct the |
|
|
813 | Coro object. |
|
|
814 | |
|
|
815 | =item $coro->safe_cancel ($arg...) |
|
|
816 | |
|
|
817 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
818 | consequently, can fail with an exception in cases the thread is not in a |
|
|
819 | cancellable state. |
|
|
820 | |
|
|
821 | This method works a bit like throwing an exception that cannot be caught |
|
|
822 | - specifically, it will clean up the thread from within itself, so |
|
|
823 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
824 | context and can block if they wish. The downside is that there is no |
|
|
825 | guarantee that the thread can be cancelled when you call this method, and |
|
|
826 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
827 | C<terminate>. |
|
|
828 | |
|
|
829 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
830 | or it has no C context attached and is inside an SLF function. |
|
|
831 | |
|
|
832 | The latter two basically mean that the thread isn't currently inside a |
|
|
833 | perl callback called from some C function (usually via some XS modules) |
|
|
834 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
835 | API). |
|
|
836 | |
|
|
837 | This call returns true when it could cancel the thread, or croaks with an |
|
|
838 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
839 | |
|
|
840 | Why the weird interface? Well, there are two common models on how and |
|
|
841 | when to cancel things. In the first, you have the expectation that your |
|
|
842 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
843 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
844 | croaks to notify of the bug. |
|
|
845 | |
|
|
846 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
847 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
848 | relatively easy like this: |
|
|
849 | |
|
|
850 | if (! eval { $coro->safe_cancel }) { |
|
|
851 | warn "unable to cancel thread: $@"; |
519 | } |
852 | } |
520 | } |
853 | |
|
|
854 | However, what you never should do is first try to cancel "safely" and |
|
|
855 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
856 | no sense: either you rely on being able to execute cleanup code in your |
|
|
857 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
858 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
859 | direct. |
521 | |
860 | |
522 | =item $coro->schedule_to |
861 | =item $coro->schedule_to |
523 | |
862 | |
524 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
863 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
525 | of continuing with the next coro from the ready queue, always switch to |
864 | of continuing with the next coro from the ready queue, always switch to |
… | |
… | |
544 | inside the coro at the next convenient point in time. Otherwise |
883 | inside the coro at the next convenient point in time. Otherwise |
545 | clears the exception object. |
884 | clears the exception object. |
546 | |
885 | |
547 | Coro will check for the exception each time a schedule-like-function |
886 | Coro will check for the exception each time a schedule-like-function |
548 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
887 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
549 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
888 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
550 | detect this case and return early in case an exception is pending. |
889 | that are part of Coro itself) detect this case and return early in case an |
|
|
890 | exception is pending. |
551 | |
891 | |
552 | The exception object will be thrown "as is" with the specified scalar in |
892 | The exception object will be thrown "as is" with the specified scalar in |
553 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
893 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
554 | (unlike with C<die>). |
894 | (unlike with C<die>). |
555 | |
895 | |
556 | This can be used as a softer means than C<cancel> to ask a coro to |
896 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
557 | end itself, although there is no guarantee that the exception will lead to |
897 | >to ask a coro to end itself, although there is no guarantee that the |
558 | termination, and if the exception isn't caught it might well end the whole |
898 | exception will lead to termination, and if the exception isn't caught it |
559 | program. |
899 | might well end the whole program. |
560 | |
900 | |
561 | You might also think of C<throw> as being the moral equivalent of |
901 | You might also think of C<throw> as being the moral equivalent of |
562 | C<kill>ing a coro with a signal (in this case, a scalar). |
902 | C<kill>ing a coro with a signal (in this case, a scalar). |
563 | |
903 | |
564 | =item $coro->join |
904 | =item $coro->join |
565 | |
905 | |
566 | Wait until the coro terminates and return any values given to the |
906 | Wait until the coro terminates and return any values given to the |
567 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
907 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
568 | from multiple coro, and all will be resumed and given the status |
908 | from multiple threads, and all will be resumed and given the status |
569 | return once the C<$coro> terminates. |
909 | return once the C<$coro> terminates. |
570 | |
910 | |
571 | =cut |
|
|
572 | |
|
|
573 | sub join { |
|
|
574 | my $self = shift; |
|
|
575 | |
|
|
576 | unless ($self->{_status}) { |
|
|
577 | my $current = $current; |
|
|
578 | |
|
|
579 | push @{$self->{_on_destroy}}, sub { |
|
|
580 | $current->ready; |
|
|
581 | undef $current; |
|
|
582 | }; |
|
|
583 | |
|
|
584 | &schedule while $current; |
|
|
585 | } |
|
|
586 | |
|
|
587 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
588 | } |
|
|
589 | |
|
|
590 | =item $coro->on_destroy (\&cb) |
911 | =item $coro->on_destroy (\&cb) |
591 | |
912 | |
592 | Registers a callback that is called when this coro gets destroyed, |
913 | Registers a callback that is called when this coro thread gets destroyed, |
593 | but before it is joined. The callback gets passed the terminate arguments, |
914 | that is, after it's resources have been freed but before it is joined. The |
|
|
915 | callback gets passed the terminate/cancel arguments, if any, and I<must |
594 | if any, and I<must not> die, under any circumstances. |
916 | not> die, under any circumstances. |
595 | |
917 | |
596 | =cut |
918 | There can be any number of C<on_destroy> callbacks per coro, and there is |
597 | |
919 | no way currently to remove a callback once added. |
598 | sub on_destroy { |
|
|
599 | my ($self, $cb) = @_; |
|
|
600 | |
|
|
601 | push @{ $self->{_on_destroy} }, $cb; |
|
|
602 | } |
|
|
603 | |
920 | |
604 | =item $oldprio = $coro->prio ($newprio) |
921 | =item $oldprio = $coro->prio ($newprio) |
605 | |
922 | |
606 | Sets (or gets, if the argument is missing) the priority of the |
923 | Sets (or gets, if the argument is missing) the priority of the |
607 | coro. Higher priority coro get run before lower priority |
924 | coro thread. Higher priority coro get run before lower priority |
608 | coro. Priorities are small signed integers (currently -4 .. +3), |
925 | coros. Priorities are small signed integers (currently -4 .. +3), |
609 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
926 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
610 | to get then): |
927 | to get then): |
611 | |
928 | |
612 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
929 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
613 | 3 > 1 > 0 > -1 > -3 > -4 |
930 | 3 > 1 > 0 > -1 > -3 > -4 |
614 | |
931 | |
615 | # set priority to HIGH |
932 | # set priority to HIGH |
616 | current->prio (PRIO_HIGH); |
933 | current->prio (PRIO_HIGH); |
617 | |
934 | |
618 | The idle coro ($Coro::idle) always has a lower priority than any |
935 | The idle coro thread ($Coro::idle) always has a lower priority than any |
619 | existing coro. |
936 | existing coro. |
620 | |
937 | |
621 | Changing the priority of the current coro will take effect immediately, |
938 | Changing the priority of the current coro will take effect immediately, |
622 | but changing the priority of coro in the ready queue (but not |
939 | 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 |
940 | 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. |
941 | bug that will be fixed in some future version. |
625 | |
942 | |
626 | =item $newprio = $coro->nice ($change) |
943 | =item $newprio = $coro->nice ($change) |
627 | |
944 | |
628 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
945 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
629 | higher values mean lower priority, just as in unix). |
946 | higher values mean lower priority, just as in UNIX's nice command). |
630 | |
947 | |
631 | =item $olddesc = $coro->desc ($newdesc) |
948 | =item $olddesc = $coro->desc ($newdesc) |
632 | |
949 | |
633 | Sets (or gets in case the argument is missing) the description for this |
950 | 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 |
951 | coro thread. This is just a free-form string you can associate with a |
635 | coro. |
952 | coro. |
636 | |
953 | |
637 | This method simply sets the C<< $coro->{desc} >> member to the given |
954 | This method simply sets the C<< $coro->{desc} >> member to the given |
638 | string. You can modify this member directly if you wish. |
955 | string. You can modify this member directly if you wish, and in fact, this |
|
|
956 | is often preferred to indicate major processing states that can then be |
|
|
957 | seen for example in a L<Coro::Debug> session: |
|
|
958 | |
|
|
959 | sub my_long_function { |
|
|
960 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
961 | ... |
|
|
962 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
963 | ... |
|
|
964 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
965 | ... |
|
|
966 | } |
639 | |
967 | |
640 | =cut |
968 | =cut |
641 | |
969 | |
642 | sub desc { |
970 | sub desc { |
643 | my $old = $_[0]{desc}; |
971 | my $old = $_[0]{desc}; |
… | |
… | |
680 | returning a new coderef. Unblocking means that calling the new coderef |
1008 | returning a new coderef. Unblocking means that calling the new coderef |
681 | will return immediately without blocking, returning nothing, while the |
1009 | will return immediately without blocking, returning nothing, while the |
682 | original code ref will be called (with parameters) from within another |
1010 | original code ref will be called (with parameters) from within another |
683 | coro. |
1011 | coro. |
684 | |
1012 | |
685 | The reason this function exists is that many event libraries (such as the |
1013 | The reason this function exists is that many event libraries (such as |
686 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
1014 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
687 | of reentrancy). This means you must not block within event callbacks, |
1015 | of reentrancy). This means you must not block within event callbacks, |
688 | otherwise you might suffer from crashes or worse. The only event library |
1016 | otherwise you might suffer from crashes or worse. The only event library |
689 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
1017 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
1018 | you might still run into deadlocks if all event loops are blocked). |
|
|
1019 | |
|
|
1020 | Coro will try to catch you when you block in the event loop |
|
|
1021 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
1022 | only works when you do not run your own event loop. |
690 | |
1023 | |
691 | This function allows your callbacks to block by executing them in another |
1024 | 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 |
1025 | 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 |
1026 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
694 | disk, for example. |
1027 | disk, for example. |
… | |
… | |
736 | unshift @unblock_queue, [$cb, @_]; |
1069 | unshift @unblock_queue, [$cb, @_]; |
737 | $unblock_scheduler->ready; |
1070 | $unblock_scheduler->ready; |
738 | } |
1071 | } |
739 | } |
1072 | } |
740 | |
1073 | |
741 | =item $cb = Coro::rouse_cb |
1074 | =item $cb = rouse_cb |
742 | |
1075 | |
743 | Create and return a "rouse callback". That's a code reference that, |
1076 | Create and return a "rouse callback". That's a code reference that, |
744 | when called, will remember a copy of its arguments and notify the owner |
1077 | when called, will remember a copy of its arguments and notify the owner |
745 | coro of the callback. |
1078 | coro of the callback. |
746 | |
1079 | |
747 | See the next function. |
1080 | See the next function. |
748 | |
1081 | |
749 | =item @args = Coro::rouse_wait [$cb] |
1082 | =item @args = rouse_wait [$cb] |
750 | |
1083 | |
751 | Wait for the specified rouse callback (or the last one that was created in |
1084 | Wait for the specified rouse callback (or the last one that was created in |
752 | this coro). |
1085 | this coro). |
753 | |
1086 | |
754 | As soon as the callback is invoked (or when the callback was invoked |
1087 | As soon as the callback is invoked (or when the callback was invoked |
… | |
… | |
761 | |
1094 | |
762 | =back |
1095 | =back |
763 | |
1096 | |
764 | =cut |
1097 | =cut |
765 | |
1098 | |
|
|
1099 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1100 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1101 | |
|
|
1102 | *{"Coro::$module\::new"} = sub { |
|
|
1103 | require "Coro/$module.pm"; |
|
|
1104 | |
|
|
1105 | # some modules have their new predefined in State.xs, some don't |
|
|
1106 | *{"Coro::$module\::new"} = $old |
|
|
1107 | if $old; |
|
|
1108 | |
|
|
1109 | goto &{"Coro::$module\::new"}; |
|
|
1110 | }; |
|
|
1111 | } |
|
|
1112 | |
766 | 1; |
1113 | 1; |
767 | |
1114 | |
768 | =head1 HOW TO WAIT FOR A CALLBACK |
1115 | =head1 HOW TO WAIT FOR A CALLBACK |
769 | |
1116 | |
770 | It is very common for a coro to wait for some callback to be |
1117 | It is very common for a coro to wait for some callback to be |
… | |
… | |
806 | my ($rpid, $rstatus) = Coro::rouse_wait; |
1153 | my ($rpid, $rstatus) = Coro::rouse_wait; |
807 | $rstatus |
1154 | $rstatus |
808 | } |
1155 | } |
809 | |
1156 | |
810 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
1157 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
811 | you can roll your own, using C<schedule>: |
1158 | you can roll your own, using C<schedule> and C<ready>: |
812 | |
1159 | |
813 | sub wait_for_child($) { |
1160 | sub wait_for_child($) { |
814 | my ($pid) = @_; |
1161 | my ($pid) = @_; |
815 | |
1162 | |
816 | # store the current coro in $current, |
1163 | # store the current coro in $current, |
… | |
… | |
819 | my ($done, $rstatus); |
1166 | my ($done, $rstatus); |
820 | |
1167 | |
821 | # pass a closure to ->child |
1168 | # pass a closure to ->child |
822 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
1169 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
823 | $rstatus = $_[1]; # remember rstatus |
1170 | $rstatus = $_[1]; # remember rstatus |
824 | $done = 1; # mark $rstatus as valud |
1171 | $done = 1; # mark $rstatus as valid |
|
|
1172 | $current->ready; # wake up the waiting thread |
825 | }); |
1173 | }); |
826 | |
1174 | |
827 | # wait until the closure has been called |
1175 | # wait until the closure has been called |
828 | schedule while !$done; |
1176 | schedule while !$done; |
829 | |
1177 | |
… | |
… | |
849 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1197 | future to allow per-thread schedulers, but Coro::State does not yet allow |
850 | this). I recommend disabling thread support and using processes, as having |
1198 | this). I recommend disabling thread support and using processes, as having |
851 | the windows process emulation enabled under unix roughly halves perl |
1199 | the windows process emulation enabled under unix roughly halves perl |
852 | performance, even when not used. |
1200 | performance, even when not used. |
853 | |
1201 | |
|
|
1202 | Attempts to use threads created in another emulated process will crash |
|
|
1203 | ("cleanly", with a null pointer exception). |
|
|
1204 | |
854 | =item coro switching is not signal safe |
1205 | =item coro switching is not signal safe |
855 | |
1206 | |
856 | You must not switch to another coro from within a signal handler |
1207 | You must not switch to another coro from within a signal handler (only |
857 | (only relevant with %SIG - most event libraries provide safe signals). |
1208 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1209 | you are sure you are not interrupting a Coro function. |
858 | |
1210 | |
859 | That means you I<MUST NOT> call any function that might "block" the |
1211 | That means you I<MUST NOT> call any function that might "block" the |
860 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1212 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
861 | anything that calls those. Everything else, including calling C<ready>, |
1213 | anything that calls those. Everything else, including calling C<ready>, |
862 | works. |
1214 | works. |
863 | |
1215 | |
864 | =back |
1216 | =back |
865 | |
1217 | |
866 | |
1218 | |
|
|
1219 | =head1 WINDOWS PROCESS EMULATION |
|
|
1220 | |
|
|
1221 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1222 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1223 | while in the same mail making rather confused statements about perl |
|
|
1224 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1225 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1226 | it is probably not obvious to everybody). |
|
|
1227 | |
|
|
1228 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1229 | scripting languages given on the perl workshop 2009: |
|
|
1230 | |
|
|
1231 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1232 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1233 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1234 | |
|
|
1235 | It does that by using threads instead of OS processes. The difference |
|
|
1236 | between processes and threads is that threads share memory (and other |
|
|
1237 | state, such as files) between threads within a single process, while |
|
|
1238 | processes do not share anything (at least not semantically). That |
|
|
1239 | means that modifications done by one thread are seen by others, while |
|
|
1240 | modifications by one process are not seen by other processes. |
|
|
1241 | |
|
|
1242 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1243 | process, all state is copied (memory is copied physically, files and code |
|
|
1244 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1245 | the same behaviour can be achieved by using operating system processes, |
|
|
1246 | except that UNIX typically uses hardware built into the system to do this |
|
|
1247 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1248 | software (rather efficiently, but of course it is still much slower than |
|
|
1249 | dedicated hardware). |
|
|
1250 | |
|
|
1251 | As mentioned before, loading code, modifying code, modifying data |
|
|
1252 | structures and so on is only visible in the ithreads process doing the |
|
|
1253 | modification, not in other ithread processes within the same OS process. |
|
|
1254 | |
|
|
1255 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1256 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1257 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1258 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1259 | faster). |
|
|
1260 | |
|
|
1261 | Sharing data is in the i-threads model is done by transfering data |
|
|
1262 | structures between threads using copying semantics, which is very slow - |
|
|
1263 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1264 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1265 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1266 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1267 | real threads, refer to my talk for details). |
|
|
1268 | |
|
|
1269 | As summary, i-threads *use* threads to implement processes, while |
|
|
1270 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1271 | processes. I-threads slow down every perl program when enabled, and |
|
|
1272 | outside of windows, serve no (or little) practical purpose, but |
|
|
1273 | disadvantages every single-threaded Perl program. |
|
|
1274 | |
|
|
1275 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1276 | misleading as it implies that it implements some kind of thread model for |
|
|
1277 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1278 | actual use and behaviour of it much better. |
|
|
1279 | |
867 | =head1 SEE ALSO |
1280 | =head1 SEE ALSO |
868 | |
1281 | |
869 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1282 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
870 | |
1283 | |
871 | Debugging: L<Coro::Debug>. |
1284 | Debugging: L<Coro::Debug>. |