… | |
… | |
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 |
|
|
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 | And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the |
|
|
201 | coro thread from another thread: |
|
|
202 | |
|
|
203 | my $coro = async { |
|
|
204 | exit 1; |
|
|
205 | }; |
|
|
206 | |
|
|
207 | $coro->cancel; # also accepts values for ->join to retrieve |
|
|
208 | |
|
|
209 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
|
|
210 | actually exiting, and might leave C libraries and XS modules in a weird |
|
|
211 | state. Unlike other thread implementations, however, Coro is exceptionally |
|
|
212 | safe with regards to cancellation, as perl will always be in a consistent |
|
|
213 | state, and for those cases where you want to do truly marvellous things |
|
|
214 | with your coro while it is being cancelled - that is, make sure all |
|
|
215 | cleanup code is executed from the thread being cancelled - there is even a |
|
|
216 | C<< ->safe_cancel >> method. |
|
|
217 | |
|
|
218 | So, cancelling a thread that runs in an XS event loop might not be the |
|
|
219 | best idea, but any other combination that deals with perl only (cancelling |
|
|
220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
|
|
221 | safe. |
|
|
222 | |
|
|
223 | Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
|
|
224 | automatically - just like other objects in Perl. This is not such a common |
|
|
225 | case, however - a running thread is referencedy b C<$Coro::current>, a |
|
|
226 | thread ready to run is referenced by the ready queue, a thread waiting |
|
|
227 | on a lock or semaphore is referenced by being in some wait list and so |
|
|
228 | on. But a thread that isn't in any of those queues gets cancelled: |
|
|
229 | |
|
|
230 | async { |
|
|
231 | schedule; # cede to other coros, don't go into the ready queue |
|
|
232 | }; |
|
|
233 | |
|
|
234 | cede; |
|
|
235 | # now the async above is destroyed, as it is not referenced by anything. |
|
|
236 | |
|
|
237 | =item 5. Cleanup |
|
|
238 | |
|
|
239 | Threads will allocate various resources. Most but not all will be returned |
|
|
240 | when a thread terminates, during clean-up. |
|
|
241 | |
|
|
242 | Cleanup is quite similar to throwing an uncaught exception: perl will |
|
|
243 | work it's way up through all subroutine calls and blocks. On it's way, it |
|
|
244 | will release all C<my> variables, undo all C<local>'s and free any other |
|
|
245 | resources truly local to the thread. |
|
|
246 | |
|
|
247 | So, a common way to free resources is to keep them referenced only by my |
|
|
248 | variables: |
|
|
249 | |
|
|
250 | async { |
|
|
251 | my $big_cache = new Cache ...; |
|
|
252 | }; |
|
|
253 | |
|
|
254 | If there are no other references, then the C<$big_cache> object will be |
|
|
255 | freed when the thread terminates, regardless of how it does so. |
|
|
256 | |
|
|
257 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
|
|
258 | resources, but that's where the C<guard> methods come in handy: |
|
|
259 | |
|
|
260 | my $sem = new Coro::Semaphore; |
|
|
261 | |
|
|
262 | async { |
|
|
263 | my $lock_guard = $sem->guard; |
|
|
264 | # if we reutrn, or die or get cancelled, here, |
|
|
265 | # then the semaphore will be "up"ed. |
|
|
266 | }; |
|
|
267 | |
|
|
268 | The C<Guard::guard> function comes in handy for any custom cleanup you |
|
|
269 | might want to do (but you cannot switch to other coroutines form those |
|
|
270 | code blocks): |
|
|
271 | |
|
|
272 | async { |
|
|
273 | my $window = new Gtk2::Window "toplevel"; |
|
|
274 | # The window will not be cleaned up automatically, even when $window |
|
|
275 | # gets freed, so use a guard to ensure it's destruction |
|
|
276 | # in case of an error: |
|
|
277 | my $window_guard = Guard::guard { $window->destroy }; |
|
|
278 | |
|
|
279 | # we are safe here |
|
|
280 | }; |
|
|
281 | |
|
|
282 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
|
|
283 | replacing the coro thread description: |
|
|
284 | |
|
|
285 | sub myfunction { |
|
|
286 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
|
|
287 | |
|
|
288 | # if we return or die here, the description will be restored |
|
|
289 | } |
|
|
290 | |
|
|
291 | =item 6. Viva La Zombie Muerte |
|
|
292 | |
|
|
293 | Even after a thread has terminated and cleaned up its resources, the Coro |
|
|
294 | object still is there and stores the return values of the thread. |
|
|
295 | |
|
|
296 | The means the Coro object gets freed automatically when the thread has |
|
|
297 | terminated and cleaned up and there arenot other references. |
|
|
298 | |
|
|
299 | If there are, the Coro object will stay around, and you can call C<< |
|
|
300 | ->join >> as many times as you wish to retrieve the result values: |
|
|
301 | |
|
|
302 | async { |
|
|
303 | print "hi\n"; |
|
|
304 | 1 |
|
|
305 | }; |
|
|
306 | |
|
|
307 | # run the async above, and free everything before returning |
|
|
308 | # from Coro::cede: |
|
|
309 | Coro::cede; |
|
|
310 | |
|
|
311 | { |
|
|
312 | my $coro = async { |
|
|
313 | print "hi\n"; |
|
|
314 | 1 |
|
|
315 | }; |
|
|
316 | |
|
|
317 | # run the async above, and clean up, but do not free the coro |
|
|
318 | # object: |
|
|
319 | Coro::cede; |
|
|
320 | |
|
|
321 | # optionally retrieve the result values |
|
|
322 | my @results = $coro->join; |
|
|
323 | |
|
|
324 | # now $coro goes out of scope, and presumably gets freed |
|
|
325 | }; |
|
|
326 | |
|
|
327 | =back |
|
|
328 | |
68 | =cut |
329 | =cut |
69 | |
330 | |
70 | package Coro; |
331 | package Coro; |
71 | |
332 | |
72 | use strict qw(vars subs); |
333 | use common::sense; |
73 | no warnings "uninitialized"; |
334 | |
|
|
335 | use Carp (); |
74 | |
336 | |
75 | use Guard (); |
337 | use Guard (); |
76 | |
338 | |
77 | use Coro::State; |
339 | use Coro::State; |
78 | |
340 | |
… | |
… | |
80 | |
342 | |
81 | our $idle; # idle handler |
343 | our $idle; # idle handler |
82 | our $main; # main coro |
344 | our $main; # main coro |
83 | our $current; # current coro |
345 | our $current; # current coro |
84 | |
346 | |
85 | our $VERSION = 5.13; |
347 | our $VERSION = 5.372; |
86 | |
348 | |
87 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
349 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
88 | our %EXPORT_TAGS = ( |
350 | our %EXPORT_TAGS = ( |
89 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
351 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
90 | ); |
352 | ); |
91 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
353 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
92 | |
354 | |
… | |
… | |
123 | |
385 | |
124 | This variable is mainly useful to integrate Coro into event loops. It is |
386 | 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 |
387 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
126 | pretty low-level functionality. |
388 | pretty low-level functionality. |
127 | |
389 | |
128 | This variable stores either a Coro object or a callback. |
390 | This variable stores a Coro object that is put into the ready queue when |
|
|
391 | there are no other ready threads (without invoking any ready hooks). |
129 | |
392 | |
130 | If it is a callback, the it is called whenever the scheduler finds no |
393 | The default implementation dies with "FATAL: deadlock detected.", followed |
131 | ready coros to run. The default implementation prints "FATAL: |
394 | 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 | |
395 | |
139 | This hook is overwritten by modules such as C<Coro::EV> and |
396 | 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 |
397 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
141 | coro so the scheduler can run it. |
398 | coro so the scheduler can run it. |
142 | |
399 | |
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 |
400 | 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 | |
401 | |
155 | =cut |
402 | =cut |
156 | |
403 | |
157 | $idle = sub { |
404 | # ||= because other modules could have provided their own by now |
158 | require Carp; |
405 | $idle ||= new Coro sub { |
159 | Carp::croak ("FATAL: deadlock detected"); |
406 | require Coro::Debug; |
|
|
407 | die "FATAL: deadlock detected.\n" |
|
|
408 | . Coro::Debug::ps_listing (); |
160 | }; |
409 | }; |
161 | |
410 | |
162 | # this coro is necessary because a coro |
411 | # this coro is necessary because a coro |
163 | # cannot destroy itself. |
412 | # cannot destroy itself. |
164 | our @destroy; |
413 | our @destroy; |
165 | our $manager; |
414 | our $manager; |
166 | |
415 | |
167 | $manager = new Coro sub { |
416 | $manager = new Coro sub { |
168 | while () { |
417 | while () { |
169 | Coro::State::cancel shift @destroy |
418 | _destroy shift @destroy |
170 | while @destroy; |
419 | while @destroy; |
171 | |
420 | |
172 | &schedule; |
421 | &schedule; |
173 | } |
422 | } |
174 | }; |
423 | }; |
… | |
… | |
206 | Example: Create a new coro that just prints its arguments. |
455 | Example: Create a new coro that just prints its arguments. |
207 | |
456 | |
208 | async { |
457 | async { |
209 | print "@_\n"; |
458 | print "@_\n"; |
210 | } 1,2,3,4; |
459 | } 1,2,3,4; |
211 | |
|
|
212 | =cut |
|
|
213 | |
|
|
214 | sub async(&@) { |
|
|
215 | my $coro = new Coro @_; |
|
|
216 | $coro->ready; |
|
|
217 | $coro |
|
|
218 | } |
|
|
219 | |
460 | |
220 | =item async_pool { ... } [@args...] |
461 | =item async_pool { ... } [@args...] |
221 | |
462 | |
222 | Similar to C<async>, but uses a coro pool, so you should not call |
463 | Similar to C<async>, but uses a coro pool, so you should not call |
223 | terminate or join on it (although you are allowed to), and you get a |
464 | terminate or join on it (although you are allowed to), and you get a |
… | |
… | |
280 | =item schedule |
521 | =item schedule |
281 | |
522 | |
282 | Calls the scheduler. The scheduler will find the next coro that is |
523 | Calls the scheduler. The scheduler will find the next coro that is |
283 | to be run from the ready queue and switches to it. The next coro |
524 | to be run from the ready queue and switches to it. The next coro |
284 | to be run is simply the one with the highest priority that is longest |
525 | to be run is simply the one with the highest priority that is longest |
285 | in its ready queue. If there is no coro ready, it will clal the |
526 | in its ready queue. If there is no coro ready, it will call the |
286 | C<$Coro::idle> hook. |
527 | C<$Coro::idle> hook. |
287 | |
528 | |
288 | Please note that the current coro will I<not> be put into the ready |
529 | 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 |
530 | 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 >>, |
531 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
… | |
… | |
316 | coro, regardless of priority. This is useful sometimes to ensure |
557 | coro, regardless of priority. This is useful sometimes to ensure |
317 | progress is made. |
558 | progress is made. |
318 | |
559 | |
319 | =item terminate [arg...] |
560 | =item terminate [arg...] |
320 | |
561 | |
321 | Terminates the current coro with the given status values (see L<cancel>). |
562 | Terminates the current coro with the given status values (see |
|
|
563 | L<cancel>). The values will not be copied, but referenced directly. |
322 | |
564 | |
323 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
565 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
324 | |
566 | |
325 | These function install enter and leave winders in the current scope. The |
567 | 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 |
568 | enter block will be executed when on_enter is called and whenever the |
… | |
… | |
338 | |
580 | |
339 | These functions implement the same concept as C<dynamic-wind> in scheme |
581 | These functions implement the same concept as C<dynamic-wind> in scheme |
340 | does, and are useful when you want to localise some resource to a specific |
582 | does, and are useful when you want to localise some resource to a specific |
341 | coro. |
583 | coro. |
342 | |
584 | |
343 | They slow down coro switching considerably for coros that use |
585 | They slow down thread switching considerably for coros that use them |
344 | them (But coro switching is still reasonably fast if the handlers are |
586 | (about 40% for a BLOCK with a single assignment, so thread switching is |
345 | fast). |
587 | still reasonably fast if the handlers are fast). |
346 | |
588 | |
347 | These functions are best understood by an example: The following function |
589 | These functions are best understood by an example: The following function |
348 | will change the current timezone to "Antarctica/South_Pole", which |
590 | will change the current timezone to "Antarctica/South_Pole", which |
349 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
591 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
350 | which remember/change the current timezone and restore the previous |
592 | which remember/change the current timezone and restore the previous |
351 | value, respectively, the timezone is only changes for the coro that |
593 | value, respectively, the timezone is only changed for the coro that |
352 | installed those handlers. |
594 | installed those handlers. |
353 | |
595 | |
354 | use POSIX qw(tzset); |
596 | use POSIX qw(tzset); |
355 | |
597 | |
356 | async { |
598 | async { |
… | |
… | |
373 | }; |
615 | }; |
374 | |
616 | |
375 | This can be used to localise about any resource (locale, uid, current |
617 | This can be used to localise about any resource (locale, uid, current |
376 | working directory etc.) to a block, despite the existance of other |
618 | working directory etc.) to a block, despite the existance of other |
377 | coros. |
619 | coros. |
|
|
620 | |
|
|
621 | Another interesting example implements time-sliced multitasking using |
|
|
622 | interval timers (this could obviously be optimised, but does the job): |
|
|
623 | |
|
|
624 | # "timeslice" the given block |
|
|
625 | sub timeslice(&) { |
|
|
626 | use Time::HiRes (); |
|
|
627 | |
|
|
628 | Coro::on_enter { |
|
|
629 | # on entering the thread, we set an VTALRM handler to cede |
|
|
630 | $SIG{VTALRM} = sub { cede }; |
|
|
631 | # and then start the interval timer |
|
|
632 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
633 | }; |
|
|
634 | Coro::on_leave { |
|
|
635 | # on leaving the thread, we stop the interval timer again |
|
|
636 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
637 | }; |
|
|
638 | |
|
|
639 | &{+shift}; |
|
|
640 | } |
|
|
641 | |
|
|
642 | # use like this: |
|
|
643 | timeslice { |
|
|
644 | # The following is an endless loop that would normally |
|
|
645 | # monopolise the process. Since it runs in a timesliced |
|
|
646 | # environment, it will regularly cede to other threads. |
|
|
647 | while () { } |
|
|
648 | }; |
|
|
649 | |
378 | |
650 | |
379 | =item killall |
651 | =item killall |
380 | |
652 | |
381 | Kills/terminates/cancels all coros except the currently running one. |
653 | Kills/terminates/cancels all coros except the currently running one. |
382 | |
654 | |
… | |
… | |
427 | |
699 | |
428 | This ensures that the scheduler will resume this coro automatically |
700 | This ensures that the scheduler will resume this coro automatically |
429 | once all the coro of higher priority and all coro of the same |
701 | once all the coro of higher priority and all coro of the same |
430 | priority that were put into the ready queue earlier have been resumed. |
702 | priority that were put into the ready queue earlier have been resumed. |
431 | |
703 | |
|
|
704 | =item $coro->suspend |
|
|
705 | |
|
|
706 | Suspends the specified coro. A suspended coro works just like any other |
|
|
707 | coro, except that the scheduler will not select a suspended coro for |
|
|
708 | execution. |
|
|
709 | |
|
|
710 | Suspending a coro can be useful when you want to keep the coro from |
|
|
711 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
712 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
713 | |
|
|
714 | A scenario for the former would be to suspend all (other) coros after a |
|
|
715 | fork and keep them alive, so their destructors aren't called, but new |
|
|
716 | coros can be created. |
|
|
717 | |
|
|
718 | =item $coro->resume |
|
|
719 | |
|
|
720 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
721 | the coro was in the ready queue when it was suspended, it might have been |
|
|
722 | unreadied by the scheduler, so an activation might have been lost. |
|
|
723 | |
|
|
724 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
725 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
726 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
727 | that. |
|
|
728 | |
|
|
729 | =item $state->is_new |
|
|
730 | |
|
|
731 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
732 | yet. Those states basically consist of only the code reference to call and |
|
|
733 | the arguments, but consumes very little other resources. New states will |
|
|
734 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
735 | |
|
|
736 | =item $state->is_zombie |
|
|
737 | |
|
|
738 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
739 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
740 | C<safe_cancel>'ed or simply went out of scope. |
|
|
741 | |
|
|
742 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
743 | exited and only stores and exit status and no other resources is called a |
|
|
744 | "zombie". |
|
|
745 | |
432 | =item $is_ready = $coro->is_ready |
746 | =item $is_ready = $coro->is_ready |
433 | |
747 | |
434 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
748 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
435 | object gets destroyed, it will eventually be scheduled by the scheduler. |
749 | object gets destroyed, it will eventually be scheduled by the scheduler. |
436 | |
750 | |
… | |
… | |
445 | Returns true iff this Coro object has been suspended. Suspended Coros will |
759 | Returns true iff this Coro object has been suspended. Suspended Coros will |
446 | not ever be scheduled. |
760 | not ever be scheduled. |
447 | |
761 | |
448 | =item $coro->cancel (arg...) |
762 | =item $coro->cancel (arg...) |
449 | |
763 | |
450 | Terminates the given Coro and makes it return the given arguments as |
764 | Terminates the given Coro thread and makes it return the given arguments as |
451 | status (default: the empty list). Never returns if the Coro is the |
765 | status (default: an empty list). Never returns if the Coro is the |
452 | current Coro. |
766 | current Coro. |
453 | |
767 | |
454 | =cut |
768 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
769 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
770 | bad things can happen, or if the cancelled thread insists on running |
|
|
771 | complicated cleanup handlers that rely on its thread context, things will |
|
|
772 | not work. |
455 | |
773 | |
456 | sub cancel { |
774 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
457 | my $self = shift; |
775 | a thread context, and is not allowed to switch to other threads. On the |
|
|
776 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
777 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
778 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
779 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
458 | |
780 | |
459 | if ($current == $self) { |
781 | The arguments to C<< ->cancel >> are not copied, but instead will |
460 | terminate @_; |
782 | be referenced directly (e.g. if you pass C<$var> and after the call |
461 | } else { |
783 | change that variable, then you might change the return values passed to |
462 | $self->{_status} = [@_]; |
784 | e.g. C<join>, so don't do that). |
463 | Coro::State::cancel $self; |
785 | |
|
|
786 | The resources of the Coro are usually freed (or destructed) before this |
|
|
787 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
788 | in some cases the manager thread has to run first to actually destruct the |
|
|
789 | Coro object. |
|
|
790 | |
|
|
791 | =item $coro->safe_cancel ($arg...) |
|
|
792 | |
|
|
793 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
794 | consequently, can fail with an exception in cases the thread is not in a |
|
|
795 | cancellable state. |
|
|
796 | |
|
|
797 | This method works a bit like throwing an exception that cannot be caught |
|
|
798 | - specifically, it will clean up the thread from within itself, so |
|
|
799 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
800 | context and can block if they wish. The downside is that there is no |
|
|
801 | guarantee that the thread can be cancelled when you call this method, and |
|
|
802 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
803 | C<terminate>. |
|
|
804 | |
|
|
805 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
806 | or it has no C context attached and is inside an SLF function. |
|
|
807 | |
|
|
808 | The latter two basically mean that the thread isn't currently inside a |
|
|
809 | perl callback called from some C function (usually via some XS modules) |
|
|
810 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
811 | API). |
|
|
812 | |
|
|
813 | This call returns true when it could cancel the thread, or croaks with an |
|
|
814 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
815 | |
|
|
816 | Why the weird interface? Well, there are two common models on how and |
|
|
817 | when to cancel things. In the first, you have the expectation that your |
|
|
818 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
819 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
820 | croaks to notify of the bug. |
|
|
821 | |
|
|
822 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
823 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
824 | relatively easy like this: |
|
|
825 | |
|
|
826 | if (! eval { $coro->safe_cancel }) { |
|
|
827 | warn "unable to cancel thread: $@"; |
464 | } |
828 | } |
465 | } |
829 | |
|
|
830 | However, what you never should do is first try to cancel "safely" and |
|
|
831 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
832 | no sense: either you rely on being able to execute cleanup code in your |
|
|
833 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
834 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
835 | direct. |
466 | |
836 | |
467 | =item $coro->schedule_to |
837 | =item $coro->schedule_to |
468 | |
838 | |
469 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
839 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
470 | of continuing with the next coro from the ready queue, always switch to |
840 | of continuing with the next coro from the ready queue, always switch to |
… | |
… | |
489 | inside the coro at the next convenient point in time. Otherwise |
859 | inside the coro at the next convenient point in time. Otherwise |
490 | clears the exception object. |
860 | clears the exception object. |
491 | |
861 | |
492 | Coro will check for the exception each time a schedule-like-function |
862 | Coro will check for the exception each time a schedule-like-function |
493 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
863 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
494 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
864 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
495 | detect this case and return early in case an exception is pending. |
865 | that are part of Coro itself) detect this case and return early in case an |
|
|
866 | exception is pending. |
496 | |
867 | |
497 | The exception object will be thrown "as is" with the specified scalar in |
868 | The exception object will be thrown "as is" with the specified scalar in |
498 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
869 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
499 | (unlike with C<die>). |
870 | (unlike with C<die>). |
500 | |
871 | |
501 | This can be used as a softer means than C<cancel> to ask a coro to |
872 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
502 | end itself, although there is no guarantee that the exception will lead to |
873 | >to ask a coro to end itself, although there is no guarantee that the |
503 | termination, and if the exception isn't caught it might well end the whole |
874 | exception will lead to termination, and if the exception isn't caught it |
504 | program. |
875 | might well end the whole program. |
505 | |
876 | |
506 | You might also think of C<throw> as being the moral equivalent of |
877 | You might also think of C<throw> as being the moral equivalent of |
507 | C<kill>ing a coro with a signal (in this case, a scalar). |
878 | C<kill>ing a coro with a signal (in this case, a scalar). |
508 | |
879 | |
509 | =item $coro->join |
880 | =item $coro->join |
510 | |
881 | |
511 | Wait until the coro terminates and return any values given to the |
882 | Wait until the coro terminates and return any values given to the |
512 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
883 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
513 | from multiple coro, and all will be resumed and given the status |
884 | from multiple threads, and all will be resumed and given the status |
514 | return once the C<$coro> terminates. |
885 | return once the C<$coro> terminates. |
515 | |
886 | |
516 | =cut |
|
|
517 | |
|
|
518 | sub join { |
|
|
519 | my $self = shift; |
|
|
520 | |
|
|
521 | unless ($self->{_status}) { |
|
|
522 | my $current = $current; |
|
|
523 | |
|
|
524 | push @{$self->{_on_destroy}}, sub { |
|
|
525 | $current->ready; |
|
|
526 | undef $current; |
|
|
527 | }; |
|
|
528 | |
|
|
529 | &schedule while $current; |
|
|
530 | } |
|
|
531 | |
|
|
532 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
533 | } |
|
|
534 | |
|
|
535 | =item $coro->on_destroy (\&cb) |
887 | =item $coro->on_destroy (\&cb) |
536 | |
888 | |
537 | Registers a callback that is called when this coro gets destroyed, |
889 | Registers a callback that is called when this coro thread gets destroyed, |
538 | but before it is joined. The callback gets passed the terminate arguments, |
890 | that is, after it's resources have been freed but before it is joined. The |
|
|
891 | callback gets passed the terminate/cancel arguments, if any, and I<must |
539 | if any, and I<must not> die, under any circumstances. |
892 | not> die, under any circumstances. |
540 | |
893 | |
541 | =cut |
894 | There can be any number of C<on_destroy> callbacks per coro, and there is |
542 | |
895 | no way currently to remove a callback once added. |
543 | sub on_destroy { |
|
|
544 | my ($self, $cb) = @_; |
|
|
545 | |
|
|
546 | push @{ $self->{_on_destroy} }, $cb; |
|
|
547 | } |
|
|
548 | |
896 | |
549 | =item $oldprio = $coro->prio ($newprio) |
897 | =item $oldprio = $coro->prio ($newprio) |
550 | |
898 | |
551 | Sets (or gets, if the argument is missing) the priority of the |
899 | Sets (or gets, if the argument is missing) the priority of the |
552 | coro. Higher priority coro get run before lower priority |
900 | coro thread. Higher priority coro get run before lower priority |
553 | coro. Priorities are small signed integers (currently -4 .. +3), |
901 | coros. Priorities are small signed integers (currently -4 .. +3), |
554 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
902 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
555 | to get then): |
903 | to get then): |
556 | |
904 | |
557 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
905 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
558 | 3 > 1 > 0 > -1 > -3 > -4 |
906 | 3 > 1 > 0 > -1 > -3 > -4 |
559 | |
907 | |
560 | # set priority to HIGH |
908 | # set priority to HIGH |
561 | current->prio (PRIO_HIGH); |
909 | current->prio (PRIO_HIGH); |
562 | |
910 | |
563 | The idle coro ($Coro::idle) always has a lower priority than any |
911 | The idle coro thread ($Coro::idle) always has a lower priority than any |
564 | existing coro. |
912 | existing coro. |
565 | |
913 | |
566 | Changing the priority of the current coro will take effect immediately, |
914 | Changing the priority of the current coro will take effect immediately, |
567 | but changing the priority of coro in the ready queue (but not |
915 | but changing the priority of a coro in the ready queue (but not running) |
568 | running) will only take effect after the next schedule (of that |
916 | will only take effect after the next schedule (of that coro). This is a |
569 | coro). This is a bug that will be fixed in some future version. |
917 | bug that will be fixed in some future version. |
570 | |
918 | |
571 | =item $newprio = $coro->nice ($change) |
919 | =item $newprio = $coro->nice ($change) |
572 | |
920 | |
573 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
921 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
574 | higher values mean lower priority, just as in unix). |
922 | higher values mean lower priority, just as in UNIX's nice command). |
575 | |
923 | |
576 | =item $olddesc = $coro->desc ($newdesc) |
924 | =item $olddesc = $coro->desc ($newdesc) |
577 | |
925 | |
578 | Sets (or gets in case the argument is missing) the description for this |
926 | Sets (or gets in case the argument is missing) the description for this |
579 | coro. This is just a free-form string you can associate with a |
927 | coro thread. This is just a free-form string you can associate with a |
580 | coro. |
928 | coro. |
581 | |
929 | |
582 | This method simply sets the C<< $coro->{desc} >> member to the given |
930 | This method simply sets the C<< $coro->{desc} >> member to the given |
583 | string. You can modify this member directly if you wish. |
931 | string. You can modify this member directly if you wish, and in fact, this |
|
|
932 | is often preferred to indicate major processing states that cna then be |
|
|
933 | seen for example in a L<Coro::Debug> session: |
|
|
934 | |
|
|
935 | sub my_long_function { |
|
|
936 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
937 | ... |
|
|
938 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
939 | ... |
|
|
940 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
941 | ... |
|
|
942 | } |
584 | |
943 | |
585 | =cut |
944 | =cut |
586 | |
945 | |
587 | sub desc { |
946 | sub desc { |
588 | my $old = $_[0]{desc}; |
947 | my $old = $_[0]{desc}; |
… | |
… | |
625 | returning a new coderef. Unblocking means that calling the new coderef |
984 | returning a new coderef. Unblocking means that calling the new coderef |
626 | will return immediately without blocking, returning nothing, while the |
985 | will return immediately without blocking, returning nothing, while the |
627 | original code ref will be called (with parameters) from within another |
986 | original code ref will be called (with parameters) from within another |
628 | coro. |
987 | coro. |
629 | |
988 | |
630 | The reason this function exists is that many event libraries (such as the |
989 | The reason this function exists is that many event libraries (such as |
631 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
990 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
632 | of reentrancy). This means you must not block within event callbacks, |
991 | of reentrancy). This means you must not block within event callbacks, |
633 | otherwise you might suffer from crashes or worse. The only event library |
992 | otherwise you might suffer from crashes or worse. The only event library |
634 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
993 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
994 | you might still run into deadlocks if all event loops are blocked). |
|
|
995 | |
|
|
996 | Coro will try to catch you when you block in the event loop |
|
|
997 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
998 | only works when you do not run your own event loop. |
635 | |
999 | |
636 | This function allows your callbacks to block by executing them in another |
1000 | This function allows your callbacks to block by executing them in another |
637 | coro where it is safe to block. One example where blocking is handy |
1001 | coro where it is safe to block. One example where blocking is handy |
638 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1002 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
639 | disk, for example. |
1003 | disk, for example. |
… | |
… | |
681 | unshift @unblock_queue, [$cb, @_]; |
1045 | unshift @unblock_queue, [$cb, @_]; |
682 | $unblock_scheduler->ready; |
1046 | $unblock_scheduler->ready; |
683 | } |
1047 | } |
684 | } |
1048 | } |
685 | |
1049 | |
686 | =item $cb = Coro::rouse_cb |
1050 | =item $cb = rouse_cb |
687 | |
1051 | |
688 | Create and return a "rouse callback". That's a code reference that, |
1052 | Create and return a "rouse callback". That's a code reference that, |
689 | when called, will remember a copy of its arguments and notify the owner |
1053 | when called, will remember a copy of its arguments and notify the owner |
690 | coro of the callback. |
1054 | coro of the callback. |
691 | |
1055 | |
692 | See the next function. |
1056 | See the next function. |
693 | |
1057 | |
694 | =item @args = Coro::rouse_wait [$cb] |
1058 | =item @args = rouse_wait [$cb] |
695 | |
1059 | |
696 | Wait for the specified rouse callback (or the last one that was created in |
1060 | Wait for the specified rouse callback (or the last one that was created in |
697 | this coro). |
1061 | this coro). |
698 | |
1062 | |
699 | As soon as the callback is invoked (or when the callback was invoked |
1063 | As soon as the callback is invoked (or when the callback was invoked |
700 | before C<rouse_wait>), it will return the arguments originally passed to |
1064 | before C<rouse_wait>), it will return the arguments originally passed to |
701 | the rouse callback. |
1065 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
1066 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
1067 | statement at the end. |
702 | |
1068 | |
703 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
1069 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
704 | |
1070 | |
705 | =back |
1071 | =back |
706 | |
1072 | |
707 | =cut |
1073 | =cut |
|
|
1074 | |
|
|
1075 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1076 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1077 | |
|
|
1078 | *{"Coro::$module\::new"} = sub { |
|
|
1079 | require "Coro/$module.pm"; |
|
|
1080 | |
|
|
1081 | # some modules have their new predefined in State.xs, some don't |
|
|
1082 | *{"Coro::$module\::new"} = $old |
|
|
1083 | if $old; |
|
|
1084 | |
|
|
1085 | goto &{"Coro::$module\::new"}; |
|
|
1086 | }; |
|
|
1087 | } |
708 | |
1088 | |
709 | 1; |
1089 | 1; |
710 | |
1090 | |
711 | =head1 HOW TO WAIT FOR A CALLBACK |
1091 | =head1 HOW TO WAIT FOR A CALLBACK |
712 | |
1092 | |
… | |
… | |
792 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1172 | future to allow per-thread schedulers, but Coro::State does not yet allow |
793 | this). I recommend disabling thread support and using processes, as having |
1173 | this). I recommend disabling thread support and using processes, as having |
794 | the windows process emulation enabled under unix roughly halves perl |
1174 | the windows process emulation enabled under unix roughly halves perl |
795 | performance, even when not used. |
1175 | performance, even when not used. |
796 | |
1176 | |
|
|
1177 | Attempts to use threads created in another emulated process will crash |
|
|
1178 | ("cleanly", with a null pointer exception). |
|
|
1179 | |
797 | =item coro switching is not signal safe |
1180 | =item coro switching is not signal safe |
798 | |
1181 | |
799 | You must not switch to another coro from within a signal handler |
1182 | You must not switch to another coro from within a signal handler (only |
800 | (only relevant with %SIG - most event libraries provide safe signals). |
1183 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1184 | you are sure you are not interrupting a Coro function. |
801 | |
1185 | |
802 | That means you I<MUST NOT> call any function that might "block" the |
1186 | That means you I<MUST NOT> call any function that might "block" the |
803 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1187 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
804 | anything that calls those. Everything else, including calling C<ready>, |
1188 | anything that calls those. Everything else, including calling C<ready>, |
805 | works. |
1189 | works. |
806 | |
1190 | |
807 | =back |
1191 | =back |
808 | |
1192 | |
809 | |
1193 | |
|
|
1194 | =head1 WINDOWS PROCESS EMULATION |
|
|
1195 | |
|
|
1196 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1197 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1198 | while in the same mail making rather confused statements about perl |
|
|
1199 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1200 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1201 | it is probably not obvious to everybody). |
|
|
1202 | |
|
|
1203 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1204 | scripting languages given on the perl workshop 2009: |
|
|
1205 | |
|
|
1206 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1207 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1208 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1209 | |
|
|
1210 | It does that by using threads instead of OS processes. The difference |
|
|
1211 | between processes and threads is that threads share memory (and other |
|
|
1212 | state, such as files) between threads within a single process, while |
|
|
1213 | processes do not share anything (at least not semantically). That |
|
|
1214 | means that modifications done by one thread are seen by others, while |
|
|
1215 | modifications by one process are not seen by other processes. |
|
|
1216 | |
|
|
1217 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1218 | process, all state is copied (memory is copied physically, files and code |
|
|
1219 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1220 | the same behaviour can be achieved by using operating system processes, |
|
|
1221 | except that UNIX typically uses hardware built into the system to do this |
|
|
1222 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1223 | software (rather efficiently, but of course it is still much slower than |
|
|
1224 | dedicated hardware). |
|
|
1225 | |
|
|
1226 | As mentioned before, loading code, modifying code, modifying data |
|
|
1227 | structures and so on is only visible in the ithreads process doing the |
|
|
1228 | modification, not in other ithread processes within the same OS process. |
|
|
1229 | |
|
|
1230 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1231 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1232 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1233 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1234 | faster). |
|
|
1235 | |
|
|
1236 | Sharing data is in the i-threads model is done by transfering data |
|
|
1237 | structures between threads using copying semantics, which is very slow - |
|
|
1238 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1239 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1240 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1241 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1242 | real threads, refer to my talk for details). |
|
|
1243 | |
|
|
1244 | As summary, i-threads *use* threads to implement processes, while |
|
|
1245 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1246 | processes. I-threads slow down every perl program when enabled, and |
|
|
1247 | outside of windows, serve no (or little) practical purpose, but |
|
|
1248 | disadvantages every single-threaded Perl program. |
|
|
1249 | |
|
|
1250 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1251 | misleading as it implies that it implements some kind of thread model for |
|
|
1252 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1253 | actual use and behaviour of it much better. |
|
|
1254 | |
810 | =head1 SEE ALSO |
1255 | =head1 SEE ALSO |
811 | |
1256 | |
812 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1257 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
813 | |
1258 | |
814 | Debugging: L<Coro::Debug>. |
1259 | Debugging: L<Coro::Debug>. |