1 | NAME |
1 | NAME |
2 | Coro - coroutine process abstraction |
2 | Coro - the only real threads in perl |
3 | |
3 | |
4 | SYNOPSIS |
4 | SYNOPSIS |
5 | use Coro; |
5 | use Coro; |
6 | |
6 | |
7 | async { |
7 | async { |
8 | # some asynchronous thread of execution |
8 | # some asynchronous thread of execution |
9 | print "2\n"; |
9 | print "2\n"; |
10 | cede; # yield back to main |
10 | cede; # yield back to main |
11 | print "4\n"; |
11 | print "4\n"; |
12 | }; |
12 | }; |
13 | print "1\n"; |
13 | print "1\n"; |
14 | cede; # yield to coroutine |
14 | cede; # yield to coro |
15 | print "3\n"; |
15 | print "3\n"; |
16 | cede; # and again |
16 | cede; # and again |
17 | |
17 | |
18 | # use locking |
18 | # use locking |
19 | use Coro::Semaphore; |
|
|
20 | my $lock = new Coro::Semaphore; |
19 | my $lock = new Coro::Semaphore; |
21 | my $locked; |
20 | my $locked; |
22 | |
21 | |
23 | $lock->down; |
22 | $lock->down; |
24 | $locked = 1; |
23 | $locked = 1; |
25 | $lock->up; |
24 | $lock->up; |
26 | |
25 | |
27 | DESCRIPTION |
26 | DESCRIPTION |
28 | This module collection manages coroutines. Coroutines are similar to |
27 | For a tutorial-style introduction, please read the Coro::Intro manpage. |
29 | threads but don't (in general) run in parallel at the same time even on |
28 | This manpage mainly contains reference information. |
30 | SMP machines. The specific flavor of coroutine used in this module also |
29 | |
31 | guarantees you that it will not switch between coroutines unless |
30 | This module collection manages continuations in general, most often in |
|
|
31 | the form of cooperative threads (also called coros, or simply "coro" in |
|
|
32 | the documentation). They are similar to kernel threads but don't (in |
|
|
33 | general) run in parallel at the same time even on SMP machines. The |
|
|
34 | specific flavor of thread offered by this module also guarantees you |
|
|
35 | that it will not switch between threads unless necessary, at |
32 | necessary, at easily-identified points in your program, so locking and |
36 | easily-identified points in your program, so locking and parallel access |
33 | parallel access are rarely an issue, making coroutine programming much |
37 | are rarely an issue, making thread programming much safer and easier |
34 | safer and easier than threads programming. |
38 | than using other thread models. |
35 | |
39 | |
36 | Unlike a normal perl program, however, coroutines allow you to have |
40 | Unlike the so-called "Perl threads" (which are not actually real threads |
37 | multiple running interpreters that share data, which is especially |
41 | but only the windows process emulation (see section of same name for |
38 | useful to code pseudo-parallel processes and for event-based |
42 | more details) ported to UNIX, and as such act as processes), Coro |
39 | programming, such as multiple HTTP-GET requests running concurrently. |
43 | provides a full shared address space, which makes communication between |
40 | See Coro::AnyEvent to learn more. |
44 | threads very easy. And coro threads are fast, too: disabling the Windows |
|
|
45 | process emulation code in your perl and using Coro can easily result in |
|
|
46 | a two to four times speed increase for your programs. A parallel matrix |
|
|
47 | multiplication benchmark (very communication-intensive) runs over 300 |
|
|
48 | times faster on a single core than perls pseudo-threads on a quad core |
|
|
49 | using all four cores. |
41 | |
50 | |
42 | Coroutines are also useful because Perl has no support for threads (the |
51 | Coro achieves that by supporting multiple running interpreters that |
43 | so called "threads" that perl offers are nothing more than the (bad) |
52 | share data, which is especially useful to code pseudo-parallel processes |
44 | process emulation coming from the Windows platform: On standard |
53 | and for event-based programming, such as multiple HTTP-GET requests |
45 | operating systems they serve no purpose whatsoever, except by making |
54 | running concurrently. See Coro::AnyEvent to learn more on how to |
46 | your programs slow and making them use a lot of memory. Best disable |
55 | integrate Coro into an event-based environment. |
47 | them when building perl, or aks your software vendor/distributor to do |
|
|
48 | it for you). |
|
|
49 | |
56 | |
50 | In this module, coroutines are defined as "callchain + lexical variables |
57 | In this module, a thread is defined as "callchain + lexical variables + |
51 | + @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own |
58 | some package variables + C stack), that is, a thread has its own |
52 | callchain, its own set of lexicals and its own set of perls most |
59 | callchain, its own set of lexicals and its own set of perls most |
53 | important global variables (see Coro::State for more configuration). |
60 | important global variables (see Coro::State for more configuration and |
|
|
61 | background info). |
54 | |
62 | |
|
|
63 | See also the "SEE ALSO" section at the end of this document - the Coro |
|
|
64 | module family is quite large. |
|
|
65 | |
|
|
66 | CORO THREAD LIFE CYCLE |
|
|
67 | During the long and exciting (or not) life of a coro thread, it goes |
|
|
68 | through a number of states: |
|
|
69 | |
|
|
70 | 1. Creation |
|
|
71 | The first thing in the life of a coro thread is it's creation - |
|
|
72 | obviously. The typical way to create a thread is to call the "async |
|
|
73 | BLOCK" function: |
|
|
74 | |
|
|
75 | async { |
|
|
76 | # thread code goes here |
|
|
77 | }; |
|
|
78 | |
|
|
79 | You can also pass arguments, which are put in @_: |
|
|
80 | |
|
|
81 | async { |
|
|
82 | print $_[1]; # prints 2 |
|
|
83 | } 1, 2, 3; |
|
|
84 | |
|
|
85 | This creates a new coro thread and puts it into the ready queue, |
|
|
86 | meaning it will run as soon as the CPU is free for it. |
|
|
87 | |
|
|
88 | "async" will return a Coro object - you can store this for future |
|
|
89 | reference or ignore it - a thread that is running, ready to run or |
|
|
90 | waiting for some event is alive on it's own. |
|
|
91 | |
|
|
92 | Another way to create a thread is to call the "new" constructor with |
|
|
93 | a code-reference: |
|
|
94 | |
|
|
95 | new Coro sub { |
|
|
96 | # thread code goes here |
|
|
97 | }, @optional_arguments; |
|
|
98 | |
|
|
99 | This is quite similar to calling "async", but the important |
|
|
100 | difference is that the new thread is not put into the ready queue, |
|
|
101 | so the thread will not run until somebody puts it there. "async" is, |
|
|
102 | therefore, identical to this sequence: |
|
|
103 | |
|
|
104 | my $coro = new Coro sub { |
|
|
105 | # thread code goes here |
|
|
106 | }; |
|
|
107 | $coro->ready; |
|
|
108 | return $coro; |
|
|
109 | |
|
|
110 | 2. Startup |
|
|
111 | When a new coro thread is created, only a copy of the code reference |
|
|
112 | and the arguments are stored, no extra memory for stacks and so on |
|
|
113 | is allocated, keeping the coro thread in a low-memory state. |
|
|
114 | |
|
|
115 | Only when it actually starts executing will all the resources be |
|
|
116 | finally allocated. |
|
|
117 | |
|
|
118 | The optional arguments specified at coro creation are available in |
|
|
119 | @_, similar to function calls. |
|
|
120 | |
|
|
121 | 3. Running / Blocking |
|
|
122 | A lot can happen after the coro thread has started running. Quite |
|
|
123 | usually, it will not run to the end in one go (because you could use |
|
|
124 | a function instead), but it will give up the CPU regularly because |
|
|
125 | it waits for external events. |
|
|
126 | |
|
|
127 | As long as a coro thread runs, its Coro object is available in the |
|
|
128 | global variable $Coro::current. |
|
|
129 | |
|
|
130 | The low-level way to give up the CPU is to call the scheduler, which |
|
|
131 | selects a new coro thread to run: |
|
|
132 | |
|
|
133 | Coro::schedule; |
|
|
134 | |
|
|
135 | Since running threads are not in the ready queue, calling the |
|
|
136 | scheduler without doing anything else will block the coro thread |
|
|
137 | forever - you need to arrange either for the coro to put woken up |
|
|
138 | (readied) by some other event or some other thread, or you can put |
|
|
139 | it into the ready queue before scheduling: |
|
|
140 | |
|
|
141 | # this is exactly what Coro::cede does |
|
|
142 | $Coro::current->ready; |
|
|
143 | Coro::schedule; |
|
|
144 | |
|
|
145 | All the higher-level synchronisation methods (Coro::Semaphore, |
|
|
146 | Coro::rouse_*...) are actually implemented via "->ready" and |
|
|
147 | "Coro::schedule". |
|
|
148 | |
|
|
149 | While the coro thread is running it also might get assigned a |
|
|
150 | C-level thread, or the C-level thread might be unassigned from it, |
|
|
151 | as the Coro runtime wishes. A C-level thread needs to be assigned |
|
|
152 | when your perl thread calls into some C-level function and that |
|
|
153 | function in turn calls perl and perl then wants to switch |
|
|
154 | coroutines. This happens most often when you run an event loop and |
|
|
155 | block in the callback, or when perl itself calls some function such |
|
|
156 | as "AUTOLOAD" or methods via the "tie" mechanism. |
|
|
157 | |
|
|
158 | 4. Termination |
|
|
159 | Many threads actually terminate after some time. There are a number |
|
|
160 | of ways to terminate a coro thread, the simplest is returning from |
|
|
161 | the top-level code reference: |
|
|
162 | |
|
|
163 | async { |
|
|
164 | # after returning from here, the coro thread is terminated |
|
|
165 | }; |
|
|
166 | |
|
|
167 | async { |
|
|
168 | return if 0.5 < rand; # terminate a little earlier, maybe |
|
|
169 | print "got a chance to print this\n"; |
|
|
170 | # or here |
|
|
171 | }; |
|
|
172 | |
|
|
173 | Any values returned from the coroutine can be recovered using |
|
|
174 | "->join": |
|
|
175 | |
|
|
176 | my $coro = async { |
|
|
177 | "hello, world\n" # return a string |
|
|
178 | }; |
|
|
179 | |
|
|
180 | my $hello_world = $coro->join; |
|
|
181 | |
|
|
182 | print $hello_world; |
|
|
183 | |
|
|
184 | Another way to terminate is to call "Coro::terminate", which at any |
|
|
185 | subroutine call nesting level: |
|
|
186 | |
|
|
187 | async { |
|
|
188 | Coro::terminate "return value 1", "return value 2"; |
|
|
189 | }; |
|
|
190 | |
|
|
191 | Yet another way is to "->cancel" (or "->safe_cancel") the coro |
|
|
192 | thread from another thread: |
|
|
193 | |
|
|
194 | my $coro = async { |
|
|
195 | exit 1; |
|
|
196 | }; |
|
|
197 | |
|
|
198 | $coro->cancel; # also accepts values for ->join to retrieve |
|
|
199 | |
|
|
200 | Cancellation *can* be dangerous - it's a bit like calling "exit" |
|
|
201 | without actually exiting, and might leave C libraries and XS modules |
|
|
202 | in a weird state. Unlike other thread implementations, however, Coro |
|
|
203 | is exceptionally safe with regards to cancellation, as perl will |
|
|
204 | always be in a consistent state, and for those cases where you want |
|
|
205 | to do truly marvellous things with your coro while it is being |
|
|
206 | cancelled - that is, make sure all cleanup code is executed from the |
|
|
207 | thread being cancelled - there is even a "->safe_cancel" method. |
|
|
208 | |
|
|
209 | So, cancelling a thread that runs in an XS event loop might not be |
|
|
210 | the best idea, but any other combination that deals with perl only |
|
|
211 | (cancelling when a thread is in a "tie" method or an "AUTOLOAD" for |
|
|
212 | example) is safe. |
|
|
213 | |
|
|
214 | Last not least, a coro thread object that isn't referenced is |
|
|
215 | "->cancel"'ed automatically - just like other objects in Perl. This |
|
|
216 | is not such a common case, however - a running thread is referencedy |
|
|
217 | by $Coro::current, a thread ready to run is referenced by the ready |
|
|
218 | queue, a thread waiting on a lock or semaphore is referenced by |
|
|
219 | being in some wait list and so on. But a thread that isn't in any of |
|
|
220 | those queues gets cancelled: |
|
|
221 | |
|
|
222 | async { |
|
|
223 | schedule; # cede to other coros, don't go into the ready queue |
|
|
224 | }; |
|
|
225 | |
|
|
226 | cede; |
|
|
227 | # now the async above is destroyed, as it is not referenced by anything. |
|
|
228 | |
|
|
229 | A slightly embellished example might make it clearer: |
|
|
230 | |
|
|
231 | async { |
|
|
232 | my $guard = Guard::guard { print "destroyed\n" }; |
|
|
233 | schedule while 1; |
|
|
234 | }; |
|
|
235 | |
|
|
236 | cede; |
|
|
237 | |
|
|
238 | Superficially one might not expect any output - since the "async" |
|
|
239 | implements an endless loop, the $guard will not be cleaned up. |
|
|
240 | However, since the thread object returned by "async" is not stored |
|
|
241 | anywhere, the thread is initially referenced because it is in the |
|
|
242 | ready queue, when it runs it is referenced by $Coro::current, but |
|
|
243 | when it calls "schedule", it gets "cancel"ed causing the guard |
|
|
244 | object to be destroyed (see the next section), and printing it's |
|
|
245 | message. |
|
|
246 | |
|
|
247 | If this seems a bit drastic, remember that this only happens when |
|
|
248 | nothing references the thread anymore, which means there is no way |
|
|
249 | to further execute it, ever. The only options at this point are |
|
|
250 | leaking the thread, or cleaning it up, which brings us to... |
|
|
251 | |
|
|
252 | 5. Cleanup |
|
|
253 | Threads will allocate various resources. Most but not all will be |
|
|
254 | returned when a thread terminates, during clean-up. |
|
|
255 | |
|
|
256 | Cleanup is quite similar to throwing an uncaught exception: perl |
|
|
257 | will work it's way up through all subroutine calls and blocks. On |
|
|
258 | it's way, it will release all "my" variables, undo all "local"'s and |
|
|
259 | free any other resources truly local to the thread. |
|
|
260 | |
|
|
261 | So, a common way to free resources is to keep them referenced only |
|
|
262 | by my variables: |
|
|
263 | |
|
|
264 | async { |
|
|
265 | my $big_cache = new Cache ...; |
|
|
266 | }; |
|
|
267 | |
|
|
268 | If there are no other references, then the $big_cache object will be |
|
|
269 | freed when the thread terminates, regardless of how it does so. |
|
|
270 | |
|
|
271 | What it does "NOT" do is unlock any Coro::Semaphores or similar |
|
|
272 | resources, but that's where the "guard" methods come in handy: |
|
|
273 | |
|
|
274 | my $sem = new Coro::Semaphore; |
|
|
275 | |
|
|
276 | async { |
|
|
277 | my $lock_guard = $sem->guard; |
|
|
278 | # if we return, or die or get cancelled, here, |
|
|
279 | # then the semaphore will be "up"ed. |
|
|
280 | }; |
|
|
281 | |
|
|
282 | The "Guard::guard" function comes in handy for any custom cleanup |
|
|
283 | you might want to do (but you cannot switch to other coroutines from |
|
|
284 | those code blocks): |
|
|
285 | |
|
|
286 | async { |
|
|
287 | my $window = new Gtk2::Window "toplevel"; |
|
|
288 | # The window will not be cleaned up automatically, even when $window |
|
|
289 | # gets freed, so use a guard to ensure it's destruction |
|
|
290 | # in case of an error: |
|
|
291 | my $window_guard = Guard::guard { $window->destroy }; |
|
|
292 | |
|
|
293 | # we are safe here |
|
|
294 | }; |
|
|
295 | |
|
|
296 | Last not least, "local" can often be handy, too, e.g. when |
|
|
297 | temporarily replacing the coro thread description: |
|
|
298 | |
|
|
299 | sub myfunction { |
|
|
300 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
|
|
301 | |
|
|
302 | # if we return or die here, the description will be restored |
|
|
303 | } |
|
|
304 | |
|
|
305 | 6. Viva La Zombie Muerte |
|
|
306 | Even after a thread has terminated and cleaned up its resources, the |
|
|
307 | Coro object still is there and stores the return values of the |
|
|
308 | thread. |
|
|
309 | |
|
|
310 | When there are no other references, it will simply be cleaned up and |
|
|
311 | freed. |
|
|
312 | |
|
|
313 | If there areany references, the Coro object will stay around, and |
|
|
314 | you can call "->join" as many times as you wish to retrieve the |
|
|
315 | result values: |
|
|
316 | |
|
|
317 | async { |
|
|
318 | print "hi\n"; |
|
|
319 | 1 |
|
|
320 | }; |
|
|
321 | |
|
|
322 | # run the async above, and free everything before returning |
|
|
323 | # from Coro::cede: |
|
|
324 | Coro::cede; |
|
|
325 | |
|
|
326 | { |
|
|
327 | my $coro = async { |
|
|
328 | print "hi\n"; |
|
|
329 | 1 |
|
|
330 | }; |
|
|
331 | |
|
|
332 | # run the async above, and clean up, but do not free the coro |
|
|
333 | # object: |
|
|
334 | Coro::cede; |
|
|
335 | |
|
|
336 | # optionally retrieve the result values |
|
|
337 | my @results = $coro->join; |
|
|
338 | |
|
|
339 | # now $coro goes out of scope, and presumably gets freed |
|
|
340 | }; |
|
|
341 | |
|
|
342 | GLOBAL VARIABLES |
55 | $Coro::main |
343 | $Coro::main |
56 | This variable stores the coroutine object that represents the main |
344 | This variable stores the Coro object that represents the main |
57 | program. While you cna "ready" it and do most other things you can |
345 | program. While you can "ready" it and do most other things you can |
58 | do to coroutines, it is mainly useful to compare again |
346 | do to coro, it is mainly useful to compare again $Coro::current, to |
59 | $Coro::current, to see whether you are running in the main program |
347 | see whether you are running in the main program or not. |
60 | or not. |
|
|
61 | |
348 | |
62 | $Coro::current |
349 | $Coro::current |
63 | The coroutine object representing the current coroutine (the last |
350 | The Coro object representing the current coro (the last coro that |
64 | coroutine that the Coro scheduler switched to). The initial value is |
351 | the Coro scheduler switched to). The initial value is $Coro::main |
65 | $main (of course). |
352 | (of course). |
66 | |
353 | |
67 | This variable is strictly *read-only*. You can take copies of the |
354 | This variable is strictly *read-only*. You can take copies of the |
68 | value stored in it and use it as any other coroutine object, but you |
355 | value stored in it and use it as any other Coro object, but you must |
69 | must not otherwise modify the variable itself. |
356 | not otherwise modify the variable itself. |
70 | |
357 | |
71 | $Coro::idle |
358 | $Coro::idle |
72 | This variable is mainly useful to integrate Coro into event loops. |
359 | This variable is mainly useful to integrate Coro into event loops. |
73 | It is usually better to rely on Coro::AnyEvent or L"Coro::EV", as |
360 | It is usually better to rely on Coro::AnyEvent or Coro::EV, as this |
74 | this is pretty low-level functionality. |
361 | is pretty low-level functionality. |
75 | |
362 | |
76 | This variable stores a callback that is called whenever the |
363 | This variable stores a Coro object that is put into the ready queue |
77 | scheduler finds no ready coroutines to run. The default |
364 | when there are no other ready threads (without invoking any ready |
78 | implementation prints "FATAL: deadlock detected" and exits, because |
365 | hooks). |
79 | the program has no other way to continue. |
|
|
80 | |
366 | |
|
|
367 | The default implementation dies with "FATAL: deadlock detected.", |
|
|
368 | followed by a thread listing, because the program has no other way |
|
|
369 | to continue. |
|
|
370 | |
81 | This hook is overwritten by modules such as "Coro::Timer" and |
371 | This hook is overwritten by modules such as "Coro::EV" and |
82 | "Coro::AnyEvent" to wait on an external event that hopefully wake up |
372 | "Coro::AnyEvent" to wait on an external event that hopefully wakes |
83 | a coroutine so the scheduler can run it. |
373 | up a coro so the scheduler can run it. |
84 | |
374 | |
85 | Note that the callback *must not*, under any circumstances, block |
|
|
86 | the current coroutine. Normally, this is achieved by having an "idle |
|
|
87 | coroutine" that calls the event loop and then blocks again, and then |
|
|
88 | readying that coroutine in the idle handler. |
|
|
89 | |
|
|
90 | See Coro::Event or Coro::AnyEvent for examples of using this |
375 | See Coro::EV or Coro::AnyEvent for examples of using this technique. |
91 | technique. |
|
|
92 | |
376 | |
93 | Please note that if your callback recursively invokes perl (e.g. for |
|
|
94 | event handlers), then it must be prepared to be called recursively |
|
|
95 | itself. |
|
|
96 | |
|
|
97 | SIMPLE COROUTINE CREATION |
377 | SIMPLE CORO CREATION |
98 | async { ... } [@args...] |
378 | async { ... } [@args...] |
99 | Create a new coroutine and return it's coroutine object (usually |
379 | Create a new coro and return its Coro object (usually unused). The |
100 | unused). The coroutine will be put into the ready queue, so it will |
380 | coro will be put into the ready queue, so it will start running |
101 | start running automatically on the next scheduler run. |
381 | automatically on the next scheduler run. |
102 | |
382 | |
103 | The first argument is a codeblock/closure that should be executed in |
383 | The first argument is a codeblock/closure that should be executed in |
104 | the coroutine. When it returns argument returns the coroutine is |
384 | the coro. When it returns argument returns the coro is automatically |
105 | automatically terminated. |
385 | terminated. |
106 | |
386 | |
107 | The remaining arguments are passed as arguments to the closure. |
387 | The remaining arguments are passed as arguments to the closure. |
108 | |
388 | |
109 | See the "Coro::State::new" constructor for info about the coroutine |
389 | See the "Coro::State::new" constructor for info about the coro |
110 | environment in which coroutines are executed. |
390 | environment in which coro are executed. |
111 | |
391 | |
112 | Calling "exit" in a coroutine will do the same as calling exit |
392 | Calling "exit" in a coro will do the same as calling exit outside |
113 | outside the coroutine. Likewise, when the coroutine dies, the |
393 | the coro. Likewise, when the coro dies, the program will exit, just |
114 | program will exit, just as it would in the main program. |
394 | as it would in the main program. |
115 | |
395 | |
116 | If you do not want that, you can provide a default "die" handler, or |
396 | If you do not want that, you can provide a default "die" handler, or |
117 | simply avoid dieing (by use of "eval"). |
397 | simply avoid dieing (by use of "eval"). |
118 | |
398 | |
119 | Example: Create a new coroutine that just prints its arguments. |
399 | Example: Create a new coro that just prints its arguments. |
120 | |
400 | |
121 | async { |
401 | async { |
122 | print "@_\n"; |
402 | print "@_\n"; |
123 | } 1,2,3,4; |
403 | } 1,2,3,4; |
124 | |
404 | |
125 | async_pool { ... } [@args...] |
405 | async_pool { ... } [@args...] |
126 | Similar to "async", but uses a coroutine pool, so you should not |
406 | Similar to "async", but uses a coro pool, so you should not call |
127 | call terminate or join on it (although you are allowed to), and you |
407 | terminate or join on it (although you are allowed to), and you get a |
128 | get a coroutine that might have executed other code already (which |
408 | coro that might have executed other code already (which can be good |
129 | can be good or bad :). |
409 | or bad :). |
130 | |
410 | |
131 | On the plus side, this function is faster than creating (and |
411 | On the plus side, this function is about twice as fast as creating |
132 | destroying) a completly new coroutine, so if you need a lot of |
412 | (and destroying) a completely new coro, so if you need a lot of |
133 | generic coroutines in quick successsion, use "async_pool", not |
413 | generic coros in quick successsion, use "async_pool", not "async". |
134 | "async". |
|
|
135 | |
414 | |
136 | The code block is executed in an "eval" context and a warning will |
415 | The code block is executed in an "eval" context and a warning will |
137 | be issued in case of an exception instead of terminating the |
416 | be issued in case of an exception instead of terminating the |
138 | program, as "async" does. As the coroutine is being reused, stuff |
417 | program, as "async" does. As the coro is being reused, stuff like |
139 | like "on_destroy" will not work in the expected way, unless you call |
418 | "on_destroy" will not work in the expected way, unless you call |
140 | terminate or cancel, which somehow defeats the purpose of pooling |
419 | terminate or cancel, which somehow defeats the purpose of pooling |
141 | (but is fine in the exceptional case). |
420 | (but is fine in the exceptional case). |
142 | |
421 | |
143 | The priority will be reset to 0 after each run, tracing will be |
422 | The priority will be reset to 0 after each run, tracing will be |
144 | disabled, the description will be reset and the default output |
423 | disabled, the description will be reset and the default output |
145 | filehandle gets restored, so you can change all these. Otherwise the |
424 | filehandle gets restored, so you can change all these. Otherwise the |
146 | coroutine will be re-used "as-is": most notably if you change other |
425 | coro will be re-used "as-is": most notably if you change other |
147 | per-coroutine global stuff such as $/ you *must needs* revert that |
426 | per-coro global stuff such as $/ you *must needs* revert that |
148 | change, which is most simply done by using local as in: "local $/". |
427 | change, which is most simply done by using local as in: "local $/". |
149 | |
428 | |
150 | The idle pool size is limited to 8 idle coroutines (this can be |
429 | The idle pool size is limited to 8 idle coros (this can be adjusted |
151 | adjusted by changing $Coro::POOL_SIZE), but there can be as many |
430 | by changing $Coro::POOL_SIZE), but there can be as many non-idle |
152 | non-idle coros as required. |
431 | coros as required. |
153 | |
432 | |
154 | If you are concerned about pooled coroutines growing a lot because a |
433 | If you are concerned about pooled coros growing a lot because a |
155 | single "async_pool" used a lot of stackspace you can e.g. |
434 | single "async_pool" used a lot of stackspace you can e.g. |
156 | "async_pool { terminate }" once per second or so to slowly replenish |
435 | "async_pool { terminate }" once per second or so to slowly replenish |
157 | the pool. In addition to that, when the stacks used by a handler |
436 | the pool. In addition to that, when the stacks used by a handler |
158 | grows larger than 16kb (adjustable via $Coro::POOL_RSS) it will also |
437 | grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also |
159 | be destroyed. |
438 | be destroyed. |
160 | |
439 | |
161 | STATIC METHODS |
440 | STATIC METHODS |
162 | Static methods are actually functions that operate on the current |
441 | Static methods are actually functions that implicitly operate on the |
163 | coroutine. |
442 | current coro. |
164 | |
443 | |
165 | schedule |
444 | schedule |
166 | Calls the scheduler. The scheduler will find the next coroutine that |
445 | Calls the scheduler. The scheduler will find the next coro that is |
167 | is to be run from the ready queue and switches to it. The next |
446 | to be run from the ready queue and switches to it. The next coro to |
168 | coroutine to be run is simply the one with the highest priority that |
447 | be run is simply the one with the highest priority that is longest |
169 | is longest in its ready queue. If there is no coroutine ready, it |
448 | in its ready queue. If there is no coro ready, it will call the |
170 | will clal the $Coro::idle hook. |
449 | $Coro::idle hook. |
171 | |
450 | |
172 | Please note that the current coroutine will *not* be put into the |
451 | Please note that the current coro will *not* be put into the ready |
173 | ready queue, so calling this function usually means you will never |
452 | queue, so calling this function usually means you will never be |
174 | be called again unless something else (e.g. an event handler) calls |
453 | called again unless something else (e.g. an event handler) calls |
175 | "->ready", thus waking you up. |
454 | "->ready", thus waking you up. |
176 | |
455 | |
177 | This makes "schedule" *the* generic method to use to block the |
456 | This makes "schedule" *the* generic method to use to block the |
178 | current coroutine and wait for events: first you remember the |
457 | current coro and wait for events: first you remember the current |
179 | current coroutine in a variable, then arrange for some callback of |
458 | coro in a variable, then arrange for some callback of yours to call |
180 | yours to call "->ready" on that once some event happens, and last |
459 | "->ready" on that once some event happens, and last you call |
181 | you call "schedule" to put yourself to sleep. Note that a lot of |
460 | "schedule" to put yourself to sleep. Note that a lot of things can |
182 | things can wake your coroutine up, so you need to check whether the |
461 | wake your coro up, so you need to check whether the event indeed |
183 | event indeed happened, e.g. by storing the status in a variable. |
462 | happened, e.g. by storing the status in a variable. |
184 | |
463 | |
185 | The canonical way to wait on external events is this: |
464 | See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for |
186 | |
465 | callbacks. |
187 | { |
|
|
188 | # remember current coroutine |
|
|
189 | my $current = $Coro::current; |
|
|
190 | |
|
|
191 | # register a hypothetical event handler |
|
|
192 | on_event_invoke sub { |
|
|
193 | # wake up sleeping coroutine |
|
|
194 | $current->ready; |
|
|
195 | undef $current; |
|
|
196 | }; |
|
|
197 | |
|
|
198 | # call schedule until event occurred. |
|
|
199 | # in case we are woken up for other reasons |
|
|
200 | # (current still defined), loop. |
|
|
201 | Coro::schedule while $current; |
|
|
202 | } |
|
|
203 | |
466 | |
204 | cede |
467 | cede |
205 | "Cede" to other coroutines. This function puts the current coroutine |
468 | "Cede" to other coros. This function puts the current coro into the |
206 | into the ready queue and calls "schedule", which has the effect of |
469 | ready queue and calls "schedule", which has the effect of giving up |
207 | giving up the current "timeslice" to other coroutines of the same or |
470 | the current "timeslice" to other coros of the same or higher |
208 | higher priority. Once your coroutine gets its turn again it will |
471 | priority. Once your coro gets its turn again it will automatically |
209 | automatically be resumed. |
472 | be resumed. |
210 | |
473 | |
211 | This function is often called "yield" in other languages. |
474 | This function is often called "yield" in other languages. |
212 | |
475 | |
213 | Coro::cede_notself |
476 | Coro::cede_notself |
214 | Works like cede, but is not exported by default and will cede to |
477 | Works like cede, but is not exported by default and will cede to |
215 | *any* coroutine, regardless of priority. This is useful sometimes to |
478 | *any* coro, regardless of priority. This is useful sometimes to |
216 | ensure progress is made. |
479 | ensure progress is made. |
217 | |
480 | |
218 | terminate [arg...] |
481 | terminate [arg...] |
219 | Terminates the current coroutine with the given status values (see |
482 | Terminates the current coro with the given status values (see |
220 | cancel). |
483 | cancel). The values will not be copied, but referenced directly. |
|
|
484 | |
|
|
485 | Coro::on_enter BLOCK, Coro::on_leave BLOCK |
|
|
486 | These function install enter and leave winders in the current scope. |
|
|
487 | The enter block will be executed when on_enter is called and |
|
|
488 | whenever the current coro is re-entered by the scheduler, while the |
|
|
489 | leave block is executed whenever the current coro is blocked by the |
|
|
490 | scheduler, and also when the containing scope is exited (by whatever |
|
|
491 | means, be it exit, die, last etc.). |
|
|
492 | |
|
|
493 | *Neither invoking the scheduler, nor exceptions, are allowed within |
|
|
494 | those BLOCKs*. That means: do not even think about calling "die" |
|
|
495 | without an eval, and do not even think of entering the scheduler in |
|
|
496 | any way. |
|
|
497 | |
|
|
498 | Since both BLOCKs are tied to the current scope, they will |
|
|
499 | automatically be removed when the current scope exits. |
|
|
500 | |
|
|
501 | These functions implement the same concept as "dynamic-wind" in |
|
|
502 | scheme does, and are useful when you want to localise some resource |
|
|
503 | to a specific coro. |
|
|
504 | |
|
|
505 | They slow down thread switching considerably for coros that use them |
|
|
506 | (about 40% for a BLOCK with a single assignment, so thread switching |
|
|
507 | is still reasonably fast if the handlers are fast). |
|
|
508 | |
|
|
509 | These functions are best understood by an example: The following |
|
|
510 | function will change the current timezone to |
|
|
511 | "Antarctica/South_Pole", which requires a call to "tzset", but by |
|
|
512 | using "on_enter" and "on_leave", which remember/change the current |
|
|
513 | timezone and restore the previous value, respectively, the timezone |
|
|
514 | is only changed for the coro that installed those handlers. |
|
|
515 | |
|
|
516 | use POSIX qw(tzset); |
|
|
517 | |
|
|
518 | async { |
|
|
519 | my $old_tz; # store outside TZ value here |
|
|
520 | |
|
|
521 | Coro::on_enter { |
|
|
522 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
523 | |
|
|
524 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
|
525 | tzset; # enable new value |
|
|
526 | }; |
|
|
527 | |
|
|
528 | Coro::on_leave { |
|
|
529 | $ENV{TZ} = $old_tz; |
|
|
530 | tzset; # restore old value |
|
|
531 | }; |
|
|
532 | |
|
|
533 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
534 | # without disturbing the TZ of any other coro. |
|
|
535 | }; |
|
|
536 | |
|
|
537 | This can be used to localise about any resource (locale, uid, |
|
|
538 | current working directory etc.) to a block, despite the existance of |
|
|
539 | other coros. |
|
|
540 | |
|
|
541 | Another interesting example implements time-sliced multitasking |
|
|
542 | using interval timers (this could obviously be optimised, but does |
|
|
543 | the job): |
|
|
544 | |
|
|
545 | # "timeslice" the given block |
|
|
546 | sub timeslice(&) { |
|
|
547 | use Time::HiRes (); |
|
|
548 | |
|
|
549 | Coro::on_enter { |
|
|
550 | # on entering the thread, we set an VTALRM handler to cede |
|
|
551 | $SIG{VTALRM} = sub { cede }; |
|
|
552 | # and then start the interval timer |
|
|
553 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
554 | }; |
|
|
555 | Coro::on_leave { |
|
|
556 | # on leaving the thread, we stop the interval timer again |
|
|
557 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
558 | }; |
|
|
559 | |
|
|
560 | &{+shift}; |
|
|
561 | } |
|
|
562 | |
|
|
563 | # use like this: |
|
|
564 | timeslice { |
|
|
565 | # The following is an endless loop that would normally |
|
|
566 | # monopolise the process. Since it runs in a timesliced |
|
|
567 | # environment, it will regularly cede to other threads. |
|
|
568 | while () { } |
|
|
569 | }; |
221 | |
570 | |
222 | killall |
571 | killall |
223 | Kills/terminates/cancels all coroutines except the currently running |
572 | Kills/terminates/cancels all coros except the currently running one. |
224 | one. This is useful after a fork, either in the child or the parent, |
|
|
225 | as usually only one of them should inherit the running coroutines. |
|
|
226 | |
573 | |
227 | Note that while this will try to free some of the main programs |
574 | Note that while this will try to free some of the main interpreter |
228 | resources, you cannot free all of them, so if a coroutine that is |
575 | resources if the calling coro isn't the main coro, but one cannot |
229 | not the main program calls this function, there will be some |
576 | free all of them, so if a coro that is not the main coro calls this |
230 | one-time resource leak. |
577 | function, there will be some one-time resource leak. |
231 | |
578 | |
232 | COROUTINE METHODS |
579 | CORO OBJECT METHODS |
233 | These are the methods you can call on coroutine objects (or to create |
580 | These are the methods you can call on coro objects (or to create them). |
234 | them). |
|
|
235 | |
581 | |
236 | new Coro \&sub [, @args...] |
582 | new Coro \&sub [, @args...] |
237 | Create a new coroutine and return it. When the sub returns, the |
583 | Create a new coro and return it. When the sub returns, the coro |
238 | coroutine automatically terminates as if "terminate" with the |
584 | automatically terminates as if "terminate" with the returned values |
239 | returned values were called. To make the coroutine run you must |
585 | were called. To make the coro run you must first put it into the |
240 | first put it into the ready queue by calling the ready method. |
586 | ready queue by calling the ready method. |
241 | |
587 | |
242 | See "async" and "Coro::State::new" for additional info about the |
588 | See "async" and "Coro::State::new" for additional info about the |
243 | coroutine environment. |
589 | coro environment. |
244 | |
590 | |
245 | $success = $coroutine->ready |
591 | $success = $coro->ready |
246 | Put the given coroutine into the end of its ready queue (there is |
592 | Put the given coro into the end of its ready queue (there is one |
247 | one queue for each priority) and return true. If the coroutine is |
593 | queue for each priority) and return true. If the coro is already in |
248 | already in the ready queue, do nothing and return false. |
594 | the ready queue, do nothing and return false. |
249 | |
595 | |
250 | This ensures that the scheduler will resume this coroutine |
596 | This ensures that the scheduler will resume this coro automatically |
251 | automatically once all the coroutines of higher priority and all |
597 | once all the coro of higher priority and all coro of the same |
252 | coroutines of the same priority that were put into the ready queue |
598 | priority that were put into the ready queue earlier have been |
253 | earlier have been resumed. |
599 | resumed. |
254 | |
600 | |
|
|
601 | $coro->suspend |
|
|
602 | Suspends the specified coro. A suspended coro works just like any |
|
|
603 | other coro, except that the scheduler will not select a suspended |
|
|
604 | coro for execution. |
|
|
605 | |
|
|
606 | Suspending a coro can be useful when you want to keep the coro from |
|
|
607 | running, but you don't want to destroy it, or when you want to |
|
|
608 | temporarily freeze a coro (e.g. for debugging) to resume it later. |
|
|
609 | |
|
|
610 | A scenario for the former would be to suspend all (other) coros |
|
|
611 | after a fork and keep them alive, so their destructors aren't |
|
|
612 | called, but new coros can be created. |
|
|
613 | |
|
|
614 | $coro->resume |
|
|
615 | If the specified coro was suspended, it will be resumed. Note that |
|
|
616 | when the coro was in the ready queue when it was suspended, it might |
|
|
617 | have been unreadied by the scheduler, so an activation might have |
|
|
618 | been lost. |
|
|
619 | |
|
|
620 | To avoid this, it is best to put a suspended coro into the ready |
|
|
621 | queue unconditionally, as every synchronisation mechanism must |
|
|
622 | protect itself against spurious wakeups, and the one in the Coro |
|
|
623 | family certainly do that. |
|
|
624 | |
|
|
625 | $state->is_new |
|
|
626 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
627 | yet. Those states basically consist of only the code reference to |
|
|
628 | call and the arguments, but consumes very little other resources. |
|
|
629 | New states will automatically get assigned a perl interpreter when |
|
|
630 | they are transfered to. |
|
|
631 | |
|
|
632 | $state->is_zombie |
|
|
633 | Returns true iff the Coro object has been cancelled, i.e. it's |
|
|
634 | resources freed because they were "cancel"'ed, "terminate"'d, |
|
|
635 | "safe_cancel"'ed or simply went out of scope. |
|
|
636 | |
|
|
637 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
638 | exited and only stores and exit status and no other resources is |
|
|
639 | called a "zombie". |
|
|
640 | |
255 | $is_ready = $coroutine->is_ready |
641 | $is_ready = $coro->is_ready |
256 | Return whether the coroutine is currently the ready queue or not, |
642 | Returns true iff the Coro object is in the ready queue. Unless the |
|
|
643 | Coro object gets destroyed, it will eventually be scheduled by the |
|
|
644 | scheduler. |
257 | |
645 | |
|
|
646 | $is_running = $coro->is_running |
|
|
647 | Returns true iff the Coro object is currently running. Only one Coro |
|
|
648 | object can ever be in the running state (but it currently is |
|
|
649 | possible to have multiple running Coro::States). |
|
|
650 | |
|
|
651 | $is_suspended = $coro->is_suspended |
|
|
652 | Returns true iff this Coro object has been suspended. Suspended |
|
|
653 | Coros will not ever be scheduled. |
|
|
654 | |
258 | $coroutine->cancel (arg...) |
655 | $coro->cancel (arg...) |
259 | Terminates the given coroutine and makes it return the given |
656 | Terminates the given Coro thread and makes it return the given |
260 | arguments as status (default: the empty list). Never returns if the |
657 | arguments as status (default: an empty list). Never returns if the |
261 | coroutine is the current coroutine. |
658 | Coro is the current Coro. |
262 | |
659 | |
263 | $coroutine->join |
660 | This is a rather brutal way to free a coro, with some limitations - |
264 | Wait until the coroutine terminates and return any values given to |
661 | if the thread is inside a C callback that doesn't expect to be |
265 | the "terminate" or "cancel" functions. "join" can be called |
662 | canceled, bad things can happen, or if the cancelled thread insists |
266 | concurrently from multiple coroutines, and all will be resumed and |
663 | on running complicated cleanup handlers that rely on its thread |
267 | given the status return once the $coroutine terminates. |
664 | context, things will not work. |
268 | |
665 | |
269 | $coroutine->on_destroy (\&cb) |
666 | Any cleanup code being run (e.g. from "guard" blocks, destructors |
270 | Registers a callback that is called when this coroutine gets |
667 | and so on) will be run without a thread context, and is not allowed |
271 | destroyed, but before it is joined. The callback gets passed the |
668 | to switch to other threads. A common mistake is to call "->cancel" |
272 | terminate arguments, if any, and *must not* die, under any |
669 | from a destructor called by die'ing inside the thread to be |
273 | circumstances. |
670 | cancelled for example. |
274 | |
671 | |
275 | $oldprio = $coroutine->prio ($newprio) |
672 | On the plus side, "->cancel" will always clean up the thread, no |
276 | Sets (or gets, if the argument is missing) the priority of the |
673 | matter what. If your cleanup code is complex or you want to avoid |
277 | coroutine. Higher priority coroutines get run before lower priority |
674 | cancelling a C-thread that doesn't know how to clean up itself, it |
278 | coroutines. Priorities are small signed integers (currently -4 .. |
675 | can be better to "->throw" an exception, or use "->safe_cancel". |
279 | +3), that you can refer to using PRIO_xxx constants (use the import |
|
|
280 | tag :prio to get then): |
|
|
281 | |
676 | |
282 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
677 | The arguments to "->cancel" are not copied, but instead will be |
283 | 3 > 1 > 0 > -1 > -3 > -4 |
678 | referenced directly (e.g. if you pass $var and after the call change |
|
|
679 | that variable, then you might change the return values passed to |
|
|
680 | e.g. "join", so don't do that). |
284 | |
681 | |
285 | # set priority to HIGH |
682 | The resources of the Coro are usually freed (or destructed) before |
286 | current->prio(PRIO_HIGH); |
683 | this call returns, but this can be delayed for an indefinite amount |
|
|
684 | of time, as in some cases the manager thread has to run first to |
|
|
685 | actually destruct the Coro object. |
287 | |
686 | |
288 | The idle coroutine ($Coro::idle) always has a lower priority than |
687 | $coro->safe_cancel ($arg...) |
289 | any existing coroutine. |
688 | Works mostly like "->cancel", but is inherently "safer", and |
|
|
689 | consequently, can fail with an exception in cases the thread is not |
|
|
690 | in a cancellable state. Essentially, "->safe_cancel" is a "->cancel" |
|
|
691 | with extra checks before canceling. |
290 | |
692 | |
291 | Changing the priority of the current coroutine will take effect |
693 | It works a bit like throwing an exception that cannot be caught - |
292 | immediately, but changing the priority of coroutines in the ready |
694 | specifically, it will clean up the thread from within itself, so all |
293 | queue (but not running) will only take effect after the next |
695 | cleanup handlers (e.g. "guard" blocks) are run with full thread |
294 | schedule (of that coroutine). This is a bug that will be fixed in |
696 | context and can block if they wish. The downside is that there is no |
295 | some future version. |
697 | guarantee that the thread can be cancelled when you call this |
|
|
698 | method, and therefore, it might fail. It is also considerably slower |
|
|
699 | than "cancel" or "terminate". |
296 | |
700 | |
297 | $newprio = $coroutine->nice ($change) |
701 | A thread is in a safe-cancellable state if it either hasn't been run |
298 | Similar to "prio", but subtract the given value from the priority |
702 | yet, or it has no C context attached and is inside an SLF function. |
299 | (i.e. higher values mean lower priority, just as in unix). |
|
|
300 | |
703 | |
301 | $olddesc = $coroutine->desc ($newdesc) |
704 | The latter two basically mean that the thread isn't currently inside |
302 | Sets (or gets in case the argument is missing) the description for |
705 | a perl callback called from some C function (usually via some XS |
303 | this coroutine. This is just a free-form string you can associate |
706 | modules) and isn't currently executing inside some C function itself |
304 | with a coroutine. |
707 | (via Coro's XS API). |
305 | |
708 | |
306 | This method simply sets the "$coroutine->{desc}" member to the given |
709 | This call returns true when it could cancel the thread, or croaks |
307 | string. You can modify this member directly if you wish. |
710 | with an error otherwise (i.e. it either returns true or doesn't |
|
|
711 | return at all). |
308 | |
712 | |
|
|
713 | Why the weird interface? Well, there are two common models on how |
|
|
714 | and when to cancel things. In the first, you have the expectation |
|
|
715 | that your coro thread can be cancelled when you want to cancel it - |
|
|
716 | if the thread isn't cancellable, this would be a bug somewhere, so |
|
|
717 | "->safe_cancel" croaks to notify of the bug. |
|
|
718 | |
|
|
719 | In the second model you sometimes want to ask nicely to cancel a |
|
|
720 | thread, but if it's not a good time, well, then don't cancel. This |
|
|
721 | can be done relatively easy like this: |
|
|
722 | |
|
|
723 | if (! eval { $coro->safe_cancel }) { |
|
|
724 | warn "unable to cancel thread: $@"; |
|
|
725 | } |
|
|
726 | |
|
|
727 | However, what you never should do is first try to cancel "safely" |
|
|
728 | and if that fails, cancel the "hard" way with "->cancel". That makes |
|
|
729 | no sense: either you rely on being able to execute cleanup code in |
|
|
730 | your thread context, or you don't. If you do, then "->safe_cancel" |
|
|
731 | is the only way, and if you don't, then "->cancel" is always faster |
|
|
732 | and more direct. |
|
|
733 | |
|
|
734 | $coro->schedule_to |
|
|
735 | Puts the current coro to sleep (like "Coro::schedule"), but instead |
|
|
736 | of continuing with the next coro from the ready queue, always switch |
|
|
737 | to the given coro object (regardless of priority etc.). The |
|
|
738 | readyness state of that coro isn't changed. |
|
|
739 | |
|
|
740 | This is an advanced method for special cases - I'd love to hear |
|
|
741 | about any uses for this one. |
|
|
742 | |
|
|
743 | $coro->cede_to |
|
|
744 | Like "schedule_to", but puts the current coro into the ready queue. |
|
|
745 | This has the effect of temporarily switching to the given coro, and |
|
|
746 | continuing some time later. |
|
|
747 | |
|
|
748 | This is an advanced method for special cases - I'd love to hear |
|
|
749 | about any uses for this one. |
|
|
750 | |
309 | $coroutine->throw ([$scalar]) |
751 | $coro->throw ([$scalar]) |
310 | If $throw is specified and defined, it will be thrown as an |
752 | If $throw is specified and defined, it will be thrown as an |
311 | exception inside the coroutine at the next convinient point in time |
753 | exception inside the coro at the next convenient point in time. |
312 | (usually after it gains control at the next schedule/transfer/cede). |
|
|
313 | Otherwise clears the exception object. |
754 | Otherwise clears the exception object. |
|
|
755 | |
|
|
756 | Coro will check for the exception each time a schedule-like-function |
|
|
757 | returns, i.e. after each "schedule", "cede", |
|
|
758 | "Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of |
|
|
759 | those functions (all that are part of Coro itself) detect this case |
|
|
760 | and return early in case an exception is pending. |
314 | |
761 | |
315 | The exception object will be thrown "as is" with the specified |
762 | The exception object will be thrown "as is" with the specified |
316 | scalar in $@, i.e. if it is a string, no line number or newline will |
763 | scalar in $@, i.e. if it is a string, no line number or newline will |
317 | be appended (unlike with "die"). |
764 | be appended (unlike with "die"). |
318 | |
765 | |
319 | This can be used as a softer means than "cancel" to ask a coroutine |
766 | This can be used as a softer means than either "cancel" or |
320 | to end itself, although there is no guarentee that the exception |
767 | "safe_cancel "to ask a coro to end itself, although there is no |
321 | will lead to termination, and if the exception isn't caught it might |
768 | guarantee that the exception will lead to termination, and if the |
322 | well end the whole program. |
769 | exception isn't caught it might well end the whole program. |
323 | |
770 | |
|
|
771 | You might also think of "throw" as being the moral equivalent of |
|
|
772 | "kill"ing a coro with a signal (in this case, a scalar). |
|
|
773 | |
|
|
774 | $coro->join |
|
|
775 | Wait until the coro terminates and return any values given to the |
|
|
776 | "terminate" or "cancel" functions. "join" can be called concurrently |
|
|
777 | from multiple threads, and all will be resumed and given the status |
|
|
778 | return once the $coro terminates. |
|
|
779 | |
|
|
780 | $coro->on_destroy (\&cb) |
|
|
781 | Registers a callback that is called when this coro thread gets |
|
|
782 | destroyed, that is, after it's resources have been freed but before |
|
|
783 | it is joined. The callback gets passed the terminate/cancel |
|
|
784 | arguments, if any, and *must not* die, under any circumstances. |
|
|
785 | |
|
|
786 | There can be any number of "on_destroy" callbacks per coro, and |
|
|
787 | there is currently no way to remove a callback once added. |
|
|
788 | |
|
|
789 | $oldprio = $coro->prio ($newprio) |
|
|
790 | Sets (or gets, if the argument is missing) the priority of the coro |
|
|
791 | thread. Higher priority coro get run before lower priority coros. |
|
|
792 | Priorities are small signed integers (currently -4 .. +3), that you |
|
|
793 | can refer to using PRIO_xxx constants (use the import tag :prio to |
|
|
794 | get then): |
|
|
795 | |
|
|
796 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
|
|
797 | 3 > 1 > 0 > -1 > -3 > -4 |
|
|
798 | |
|
|
799 | # set priority to HIGH |
|
|
800 | current->prio (PRIO_HIGH); |
|
|
801 | |
|
|
802 | The idle coro thread ($Coro::idle) always has a lower priority than |
|
|
803 | any existing coro. |
|
|
804 | |
|
|
805 | Changing the priority of the current coro will take effect |
|
|
806 | immediately, but changing the priority of a coro in the ready queue |
|
|
807 | (but not running) will only take effect after the next schedule (of |
|
|
808 | that coro). This is a bug that will be fixed in some future version. |
|
|
809 | |
|
|
810 | $newprio = $coro->nice ($change) |
|
|
811 | Similar to "prio", but subtract the given value from the priority |
|
|
812 | (i.e. higher values mean lower priority, just as in UNIX's nice |
|
|
813 | command). |
|
|
814 | |
|
|
815 | $olddesc = $coro->desc ($newdesc) |
|
|
816 | Sets (or gets in case the argument is missing) the description for |
|
|
817 | this coro thread. This is just a free-form string you can associate |
|
|
818 | with a coro. |
|
|
819 | |
|
|
820 | This method simply sets the "$coro->{desc}" member to the given |
|
|
821 | string. You can modify this member directly if you wish, and in |
|
|
822 | fact, this is often preferred to indicate major processing states |
|
|
823 | that can then be seen for example in a Coro::Debug session: |
|
|
824 | |
|
|
825 | sub my_long_function { |
|
|
826 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
827 | ... |
|
|
828 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
829 | ... |
|
|
830 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
831 | ... |
|
|
832 | } |
|
|
833 | |
324 | GLOBAL FUNCTIONS |
834 | GLOBAL FUNCTIONS |
325 | Coro::nready |
835 | Coro::nready |
326 | Returns the number of coroutines that are currently in the ready |
836 | Returns the number of coro that are currently in the ready state, |
327 | state, i.e. that can be switched to by calling "schedule" directory |
837 | i.e. that can be switched to by calling "schedule" directory or |
328 | or indirectly. The value 0 means that the only runnable coroutine is |
838 | indirectly. The value 0 means that the only runnable coro is the |
329 | the currently running one, so "cede" would have no effect, and |
839 | currently running one, so "cede" would have no effect, and |
330 | "schedule" would cause a deadlock unless there is an idle handler |
840 | "schedule" would cause a deadlock unless there is an idle handler |
331 | that wakes up some coroutines. |
841 | that wakes up some coro. |
332 | |
842 | |
333 | my $guard = Coro::guard { ... } |
843 | my $guard = Coro::guard { ... } |
334 | This creates and returns a guard object. Nothing happens until the |
844 | This function still exists, but is deprecated. Please use the |
335 | object gets destroyed, in which case the codeblock given as argument |
845 | "Guard::guard" function instead. |
336 | will be executed. This is useful to free locks or other resources in |
|
|
337 | case of a runtime error or when the coroutine gets canceled, as in |
|
|
338 | both cases the guard block will be executed. The guard object |
|
|
339 | supports only one method, "->cancel", which will keep the codeblock |
|
|
340 | from being executed. |
|
|
341 | |
|
|
342 | Example: set some flag and clear it again when the coroutine gets |
|
|
343 | canceled or the function returns: |
|
|
344 | |
|
|
345 | sub do_something { |
|
|
346 | my $guard = Coro::guard { $busy = 0 }; |
|
|
347 | $busy = 1; |
|
|
348 | |
|
|
349 | # do something that requires $busy to be true |
|
|
350 | } |
|
|
351 | |
846 | |
352 | unblock_sub { ... } |
847 | unblock_sub { ... } |
353 | This utility function takes a BLOCK or code reference and "unblocks" |
848 | This utility function takes a BLOCK or code reference and "unblocks" |
354 | it, returning a new coderef. Unblocking means that calling the new |
849 | it, returning a new coderef. Unblocking means that calling the new |
355 | coderef will return immediately without blocking, returning nothing, |
850 | coderef will return immediately without blocking, returning nothing, |
356 | while the original code ref will be called (with parameters) from |
851 | while the original code ref will be called (with parameters) from |
357 | within another coroutine. |
852 | within another coro. |
358 | |
853 | |
359 | The reason this function exists is that many event libraries (such |
854 | The reason this function exists is that many event libraries (such |
360 | as the venerable Event module) are not coroutine-safe (a weaker form |
855 | as the venerable Event module) are not thread-safe (a weaker form of |
361 | of thread-safety). This means you must not block within event |
856 | reentrancy). This means you must not block within event callbacks, |
362 | callbacks, otherwise you might suffer from crashes or worse. The |
857 | otherwise you might suffer from crashes or worse. The only event |
363 | only event library currently known that is safe to use without |
858 | library currently known that is safe to use without "unblock_sub" is |
364 | "unblock_sub" is EV. |
859 | EV (but you might still run into deadlocks if all event loops are |
|
|
860 | blocked). |
|
|
861 | |
|
|
862 | Coro will try to catch you when you block in the event loop ("FATAL: |
|
|
863 | $Coro::idle blocked itself"), but this is just best effort and only |
|
|
864 | works when you do not run your own event loop. |
365 | |
865 | |
366 | This function allows your callbacks to block by executing them in |
866 | This function allows your callbacks to block by executing them in |
367 | another coroutine where it is safe to block. One example where |
867 | another coro where it is safe to block. One example where blocking |
368 | blocking is handy is when you use the Coro::AIO functions to save |
868 | is handy is when you use the Coro::AIO functions to save results to |
369 | results to disk, for example. |
869 | disk, for example. |
370 | |
870 | |
371 | In short: simply use "unblock_sub { ... }" instead of "sub { ... }" |
871 | In short: simply use "unblock_sub { ... }" instead of "sub { ... }" |
372 | when creating event callbacks that want to block. |
872 | when creating event callbacks that want to block. |
373 | |
873 | |
374 | If your handler does not plan to block (e.g. simply sends a message |
874 | If your handler does not plan to block (e.g. simply sends a message |
375 | to another coroutine, or puts some other coroutine into the ready |
875 | to another coro, or puts some other coro into the ready queue), |
376 | queue), there is no reason to use "unblock_sub". |
876 | there is no reason to use "unblock_sub". |
377 | |
877 | |
378 | Note that you also need to use "unblock_sub" for any other callbacks |
878 | Note that you also need to use "unblock_sub" for any other callbacks |
379 | that are indirectly executed by any C-based event loop. For example, |
879 | that are indirectly executed by any C-based event loop. For example, |
380 | when you use a module that uses AnyEvent (and you use |
880 | when you use a module that uses AnyEvent (and you use |
381 | Coro::AnyEvent) and it provides callbacks that are the result of |
881 | Coro::AnyEvent) and it provides callbacks that are the result of |
382 | some event callback, then you must not block either, or use |
882 | some event callback, then you must not block either, or use |
383 | "unblock_sub". |
883 | "unblock_sub". |
384 | |
884 | |
|
|
885 | $cb = rouse_cb |
|
|
886 | Create and return a "rouse callback". That's a code reference that, |
|
|
887 | when called, will remember a copy of its arguments and notify the |
|
|
888 | owner coro of the callback. |
|
|
889 | |
|
|
890 | See the next function. |
|
|
891 | |
|
|
892 | @args = rouse_wait [$cb] |
|
|
893 | Wait for the specified rouse callback (or the last one that was |
|
|
894 | created in this coro). |
|
|
895 | |
|
|
896 | As soon as the callback is invoked (or when the callback was invoked |
|
|
897 | before "rouse_wait"), it will return the arguments originally passed |
|
|
898 | to the rouse callback. In scalar context, that means you get the |
|
|
899 | *last* argument, just as if "rouse_wait" had a "return ($a1, $a2, |
|
|
900 | $a3...)" statement at the end. |
|
|
901 | |
|
|
902 | See the section HOW TO WAIT FOR A CALLBACK for an actual usage |
|
|
903 | example. |
|
|
904 | |
|
|
905 | HOW TO WAIT FOR A CALLBACK |
|
|
906 | It is very common for a coro to wait for some callback to be called. |
|
|
907 | This occurs naturally when you use coro in an otherwise event-based |
|
|
908 | program, or when you use event-based libraries. |
|
|
909 | |
|
|
910 | These typically register a callback for some event, and call that |
|
|
911 | callback when the event occured. In a coro, however, you typically want |
|
|
912 | to just wait for the event, simplyifying things. |
|
|
913 | |
|
|
914 | For example "AnyEvent->child" registers a callback to be called when a |
|
|
915 | specific child has exited: |
|
|
916 | |
|
|
917 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
918 | |
|
|
919 | But from within a coro, you often just want to write this: |
|
|
920 | |
|
|
921 | my $status = wait_for_child $pid; |
|
|
922 | |
|
|
923 | Coro offers two functions specifically designed to make this easy, |
|
|
924 | "rouse_cb" and "rouse_wait". |
|
|
925 | |
|
|
926 | The first function, "rouse_cb", generates and returns a callback that, |
|
|
927 | when invoked, will save its arguments and notify the coro that created |
|
|
928 | the callback. |
|
|
929 | |
|
|
930 | The second function, "rouse_wait", waits for the callback to be called |
|
|
931 | (by calling "schedule" to go to sleep) and returns the arguments |
|
|
932 | originally passed to the callback. |
|
|
933 | |
|
|
934 | Using these functions, it becomes easy to write the "wait_for_child" |
|
|
935 | function mentioned above: |
|
|
936 | |
|
|
937 | sub wait_for_child($) { |
|
|
938 | my ($pid) = @_; |
|
|
939 | |
|
|
940 | my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb); |
|
|
941 | |
|
|
942 | my ($rpid, $rstatus) = rouse_wait; |
|
|
943 | $rstatus |
|
|
944 | } |
|
|
945 | |
|
|
946 | In the case where "rouse_cb" and "rouse_wait" are not flexible enough, |
|
|
947 | you can roll your own, using "schedule" and "ready": |
|
|
948 | |
|
|
949 | sub wait_for_child($) { |
|
|
950 | my ($pid) = @_; |
|
|
951 | |
|
|
952 | # store the current coro in $current, |
|
|
953 | # and provide result variables for the closure passed to ->child |
|
|
954 | my $current = $Coro::current; |
|
|
955 | my ($done, $rstatus); |
|
|
956 | |
|
|
957 | # pass a closure to ->child |
|
|
958 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
959 | $rstatus = $_[1]; # remember rstatus |
|
|
960 | $done = 1; # mark $rstatus as valid |
|
|
961 | $current->ready; # wake up the waiting thread |
|
|
962 | }); |
|
|
963 | |
|
|
964 | # wait until the closure has been called |
|
|
965 | schedule while !$done; |
|
|
966 | |
|
|
967 | $rstatus |
|
|
968 | } |
|
|
969 | |
385 | BUGS/LIMITATIONS |
970 | BUGS/LIMITATIONS |
|
|
971 | fork with pthread backend |
|
|
972 | When Coro is compiled using the pthread backend (which isn't |
|
|
973 | recommended but required on many BSDs as their libcs are completely |
|
|
974 | broken), then coro will not survive a fork. There is no known |
|
|
975 | workaround except to fix your libc and use a saner backend. |
|
|
976 | |
|
|
977 | perl process emulation ("threads") |
386 | This module is not perl-pseudo-thread-safe. You should only ever use |
978 | This module is not perl-pseudo-thread-safe. You should only ever use |
387 | this module from the same thread (this requirement might be removed in |
979 | this module from the first thread (this requirement might be removed |
388 | the future to allow per-thread schedulers, but Coro::State does not yet |
980 | in the future to allow per-thread schedulers, but Coro::State does |
389 | allow this). I recommend disabling thread support and using processes, |
981 | not yet allow this). I recommend disabling thread support and using |
390 | as this is much faster and uses less memory. |
982 | processes, as having the windows process emulation enabled under |
|
|
983 | unix roughly halves perl performance, even when not used. |
|
|
984 | |
|
|
985 | Attempts to use threads created in another emulated process will |
|
|
986 | crash ("cleanly", with a null pointer exception). |
|
|
987 | |
|
|
988 | coro switching is not signal safe |
|
|
989 | You must not switch to another coro from within a signal handler |
|
|
990 | (only relevant with %SIG - most event libraries provide safe |
|
|
991 | signals), *unless* you are sure you are not interrupting a Coro |
|
|
992 | function. |
|
|
993 | |
|
|
994 | That means you *MUST NOT* call any function that might "block" the |
|
|
995 | current coro - "cede", "schedule" "Coro::Semaphore->down" or |
|
|
996 | anything that calls those. Everything else, including calling |
|
|
997 | "ready", works. |
|
|
998 | |
|
|
999 | WINDOWS PROCESS EMULATION |
|
|
1000 | A great many people seem to be confused about ithreads (for example, |
|
|
1001 | Chip Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1002 | while in the same mail making rather confused statements about perl |
|
|
1003 | ithreads (for example, that memory or files would be shared), showing |
|
|
1004 | his lack of understanding of this area - if it is hard to understand for |
|
|
1005 | Chip, it is probably not obvious to everybody). |
|
|
1006 | |
|
|
1007 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1008 | scripting languages given on the perl workshop 2009: |
|
|
1009 | |
|
|
1010 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1011 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1012 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1013 | |
|
|
1014 | It does that by using threads instead of OS processes. The difference |
|
|
1015 | between processes and threads is that threads share memory (and other |
|
|
1016 | state, such as files) between threads within a single process, while |
|
|
1017 | processes do not share anything (at least not semantically). That means |
|
|
1018 | that modifications done by one thread are seen by others, while |
|
|
1019 | modifications by one process are not seen by other processes. |
|
|
1020 | |
|
|
1021 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1022 | process, all state is copied (memory is copied physically, files and |
|
|
1023 | code is copied logically). Afterwards, it isolates all modifications. On |
|
|
1024 | UNIX, the same behaviour can be achieved by using operating system |
|
|
1025 | processes, except that UNIX typically uses hardware built into the |
|
|
1026 | system to do this efficiently, while the windows process emulation |
|
|
1027 | emulates this hardware in software (rather efficiently, but of course it |
|
|
1028 | is still much slower than dedicated hardware). |
|
|
1029 | |
|
|
1030 | As mentioned before, loading code, modifying code, modifying data |
|
|
1031 | structures and so on is only visible in the ithreads process doing the |
|
|
1032 | modification, not in other ithread processes within the same OS process. |
|
|
1033 | |
|
|
1034 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1035 | processes. What makes it so bad is that on non-windows platforms, you |
|
|
1036 | can actually take advantage of custom hardware for this purpose (as |
|
|
1037 | evidenced by the forks module, which gives you the (i-) threads API, |
|
|
1038 | just much faster). |
|
|
1039 | |
|
|
1040 | Sharing data is in the i-threads model is done by transfering data |
|
|
1041 | structures between threads using copying semantics, which is very slow - |
|
|
1042 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1043 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1044 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1045 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1046 | real threads, refer to my talk for details). |
|
|
1047 | |
|
|
1048 | As summary, i-threads *use* threads to implement processes, while the |
|
|
1049 | compatible forks module *uses* processes to emulate, uhm, processes. |
|
|
1050 | I-threads slow down every perl program when enabled, and outside of |
|
|
1051 | windows, serve no (or little) practical purpose, but disadvantages every |
|
|
1052 | single-threaded Perl program. |
|
|
1053 | |
|
|
1054 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1055 | misleading as it implies that it implements some kind of thread model |
|
|
1056 | for perl, and prefer the name "windows process emulation", which |
|
|
1057 | describes the actual use and behaviour of it much better. |
391 | |
1058 | |
392 | SEE ALSO |
1059 | SEE ALSO |
393 | Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event. |
1060 | Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event. |
394 | |
1061 | |
395 | Debugging: Coro::Debug. |
1062 | Debugging: Coro::Debug. |
396 | |
1063 | |
397 | Support/Utility: Coro::Specific, Coro::Util. |
1064 | Support/Utility: Coro::Specific, Coro::Util. |
398 | |
1065 | |
399 | Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
1066 | Locking and IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
400 | Coro::SemaphoreSet, Coro::RWLock. |
1067 | Coro::SemaphoreSet, Coro::RWLock. |
401 | |
1068 | |
402 | IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO. |
1069 | I/O and Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO. |
403 | |
1070 | |
404 | Compatibility: Coro::LWP, Coro::BDB, Coro::Storable, Coro::Select. |
1071 | Compatibility with other modules: Coro::LWP (but see also AnyEvent::HTTP |
|
|
1072 | for a better-working alternative), Coro::BDB, Coro::Storable, |
|
|
1073 | Coro::Select. |
405 | |
1074 | |
406 | XS API: Coro::MakeMaker. |
1075 | XS API: Coro::MakeMaker. |
407 | |
1076 | |
408 | Low level Configuration, Coroutine Environment: Coro::State. |
1077 | Low level Configuration, Thread Environment, Continuations: Coro::State. |
409 | |
1078 | |
410 | AUTHOR |
1079 | AUTHOR |
411 | Marc Lehmann <schmorp@schmorp.de> |
1080 | Marc Lehmann <schmorp@schmorp.de> |
412 | http://home.schmorp.de/ |
1081 | http://home.schmorp.de/ |
413 | |
1082 | |