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 { |
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23 | $lock->down; |
23 | $lock->down; |
24 | $locked = 1; |
24 | $locked = 1; |
25 | $lock->up; |
25 | $lock->up; |
26 | |
26 | |
27 | DESCRIPTION |
27 | DESCRIPTION |
28 | This module collection manages coroutines. Coroutines are similar to |
28 | 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 |
29 | This manpage mainly contains reference information. |
30 | SMP machines. The specific flavor of coroutine used in this module also |
30 | |
31 | guarantees you that it will not switch between coroutines unless |
31 | This module collection manages continuations in general, most often in |
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32 | the form of cooperative threads (also called coroutines in the |
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33 | documentation). They are similar to kernel threads but don't (in |
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34 | general) run in parallel at the same time even on SMP machines. The |
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35 | specific flavor of thread offered by this module also guarantees you |
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36 | that it will not switch between threads unless necessary, at |
32 | necessary, at easily-identified points in your program, so locking and |
37 | easily-identified points in your program, so locking and parallel access |
33 | parallel access are rarely an issue, making coroutine programming much |
38 | are rarely an issue, making thread programming much safer and easier |
34 | safer and easier than threads programming. |
39 | than using other thread models. |
35 | |
40 | |
36 | Unlike a normal perl program, however, coroutines allow you to have |
41 | Unlike the so-called "Perl threads" (which are not actually real threads |
37 | multiple running interpreters that share data, which is especially |
42 | but only the windows process emulation ported to unix), Coro provides a |
38 | useful to code pseudo-parallel processes and for event-based |
43 | full shared address space, which makes communication between threads |
39 | programming, such as multiple HTTP-GET requests running concurrently. |
44 | very easy. And threads are fast, too: disabling the Windows process |
40 | See Coro::AnyEvent to learn more. |
45 | emulation code in your perl and using Coro can easily result in a two to |
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46 | four times speed increase for your programs. |
41 | |
47 | |
42 | Coroutines are also useful because Perl has no support for threads (the |
48 | Coro achieves that by supporting multiple running interpreters that |
43 | so called "threads" that perl offers are nothing more than the (bad) |
49 | share data, which is especially useful to code pseudo-parallel processes |
44 | process emulation coming from the Windows platform: On standard |
50 | and for event-based programming, such as multiple HTTP-GET requests |
45 | operating systems they serve no purpose whatsoever, except by making |
51 | 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 |
52 | integrate Coro into an event-based environment. |
47 | them when building perl, or aks your software vendor/distributor to do |
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48 | it for you). |
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49 | |
53 | |
50 | In this module, coroutines are defined as "callchain + lexical variables |
54 | In this module, a thread is defined as "callchain + lexical variables + |
51 | + @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own |
55 | @_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain, |
52 | callchain, its own set of lexicals and its own set of perls most |
56 | its own set of lexicals and its own set of perls most important global |
53 | important global variables (see Coro::State for more configuration). |
57 | variables (see Coro::State for more configuration and background info). |
54 | |
58 | |
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59 | See also the "SEE ALSO" section at the end of this document - the Coro |
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60 | module family is quite large. |
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61 | |
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62 | GLOBAL VARIABLES |
55 | $Coro::main |
63 | $Coro::main |
56 | This variable stores the coroutine object that represents the main |
64 | This variable stores the coroutine object that represents the main |
57 | program. While you cna "ready" it and do most other things you can |
65 | program. While you cna "ready" it and do most other things you can |
58 | do to coroutines, it is mainly useful to compare again |
66 | do to coroutines, it is mainly useful to compare again |
59 | $Coro::current, to see whether you are running in the main program |
67 | $Coro::current, to see whether you are running in the main program |
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68 | value stored in it and use it as any other coroutine object, but you |
76 | value stored in it and use it as any other coroutine object, but you |
69 | must not otherwise modify the variable itself. |
77 | must not otherwise modify the variable itself. |
70 | |
78 | |
71 | $Coro::idle |
79 | $Coro::idle |
72 | This variable is mainly useful to integrate Coro into event loops. |
80 | 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 |
81 | It is usually better to rely on Coro::AnyEvent or Coro::EV, as this |
74 | this is pretty low-level functionality. |
82 | is pretty low-level functionality. |
75 | |
83 | |
76 | This variable stores a callback that is called whenever the |
84 | This variable stores either a coroutine or a callback. |
77 | scheduler finds no ready coroutines to run. The default |
85 | |
78 | implementation prints "FATAL: deadlock detected" and exits, because |
86 | If it is a callback, the it is called whenever the scheduler finds |
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87 | no ready coroutines to run. The default implementation prints |
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88 | "FATAL: deadlock detected" and exits, because the program has no |
79 | the program has no other way to continue. |
89 | other way to continue. |
80 | |
90 | |
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91 | If it is a coroutine object, then this object will be readied |
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92 | (without invoking any ready hooks, however) when the scheduler finds |
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93 | no other ready coroutines to run. |
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94 | |
81 | This hook is overwritten by modules such as "Coro::Timer" and |
95 | This hook is overwritten by modules such as "Coro::EV" and |
82 | "Coro::AnyEvent" to wait on an external event that hopefully wake up |
96 | "Coro::AnyEvent" to wait on an external event that hopefully wake up |
83 | a coroutine so the scheduler can run it. |
97 | a coroutine so the scheduler can run it. |
84 | |
98 | |
85 | Note that the callback *must not*, under any circumstances, block |
99 | Note that the callback *must not*, under any circumstances, block |
86 | the current coroutine. Normally, this is achieved by having an "idle |
100 | the current coroutine. Normally, this is achieved by having an "idle |
87 | coroutine" that calls the event loop and then blocks again, and then |
101 | coroutine" that calls the event loop and then blocks again, and then |
88 | readying that coroutine in the idle handler. |
102 | readying that coroutine in the idle handler, or by simply placing |
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103 | the idle coroutine in this variable. |
89 | |
104 | |
90 | See Coro::Event or Coro::AnyEvent for examples of using this |
105 | See Coro::Event or Coro::AnyEvent for examples of using this |
91 | technique. |
106 | technique. |
92 | |
107 | |
93 | Please note that if your callback recursively invokes perl (e.g. for |
108 | Please note that if your callback recursively invokes perl (e.g. for |
94 | event handlers), then it must be prepared to be called recursively |
109 | event handlers), then it must be prepared to be called recursively |
95 | itself. |
110 | itself. |
96 | |
111 | |
97 | SIMPLE COROUTINE CREATION |
112 | SIMPLE COROUTINE CREATION |
98 | async { ... } [@args...] |
113 | async { ... } [@args...] |
99 | Create a new coroutine and return it's coroutine object (usually |
114 | Create a new coroutine and return its coroutine object (usually |
100 | unused). The coroutine will be put into the ready queue, so it will |
115 | unused). The coroutine will be put into the ready queue, so it will |
101 | start running automatically on the next scheduler run. |
116 | start running automatically on the next scheduler run. |
102 | |
117 | |
103 | The first argument is a codeblock/closure that should be executed in |
118 | The first argument is a codeblock/closure that should be executed in |
104 | the coroutine. When it returns argument returns the coroutine is |
119 | the coroutine. When it returns argument returns the coroutine is |
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153 | |
168 | |
154 | If you are concerned about pooled coroutines growing a lot because a |
169 | If you are concerned about pooled coroutines growing a lot because a |
155 | single "async_pool" used a lot of stackspace you can e.g. |
170 | single "async_pool" used a lot of stackspace you can e.g. |
156 | "async_pool { terminate }" once per second or so to slowly replenish |
171 | "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 |
172 | 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 |
173 | grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also |
159 | be destroyed. |
174 | be destroyed. |
160 | |
175 | |
161 | STATIC METHODS |
176 | STATIC METHODS |
162 | Static methods are actually functions that operate on the current |
177 | Static methods are actually functions that implicitly operate on the |
163 | coroutine. |
178 | current coroutine. |
164 | |
179 | |
165 | schedule |
180 | schedule |
166 | Calls the scheduler. The scheduler will find the next coroutine that |
181 | Calls the scheduler. The scheduler will find the next coroutine that |
167 | is to be run from the ready queue and switches to it. The next |
182 | is to be run from the ready queue and switches to it. The next |
168 | coroutine to be run is simply the one with the highest priority that |
183 | coroutine to be run is simply the one with the highest priority that |
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211 | Note that while this will try to free some of the main programs |
226 | Note that while this will try to free some of the main programs |
212 | resources, you cannot free all of them, so if a coroutine that is |
227 | resources, you cannot free all of them, so if a coroutine that is |
213 | not the main program calls this function, there will be some |
228 | not the main program calls this function, there will be some |
214 | one-time resource leak. |
229 | one-time resource leak. |
215 | |
230 | |
216 | COROUTINE METHODS |
231 | COROUTINE OBJECT METHODS |
217 | These are the methods you can call on coroutine objects (or to create |
232 | These are the methods you can call on coroutine objects (or to create |
218 | them). |
233 | them). |
219 | |
234 | |
220 | new Coro \&sub [, @args...] |
235 | new Coro \&sub [, @args...] |
221 | Create a new coroutine and return it. When the sub returns, the |
236 | Create a new coroutine and return it. When the sub returns, the |
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328 | with a coroutine. |
343 | with a coroutine. |
329 | |
344 | |
330 | This method simply sets the "$coroutine->{desc}" member to the given |
345 | This method simply sets the "$coroutine->{desc}" member to the given |
331 | string. You can modify this member directly if you wish. |
346 | string. You can modify this member directly if you wish. |
332 | |
347 | |
333 | GLOBAL FUNCTIONS |
348 | GLOBAL FUNCTIONS |
334 | Coro::nready |
349 | Coro::nready |
335 | Returns the number of coroutines that are currently in the ready |
350 | Returns the number of coroutines that are currently in the ready |
336 | state, i.e. that can be switched to by calling "schedule" directory |
351 | state, i.e. that can be switched to by calling "schedule" directory |
337 | or indirectly. The value 0 means that the only runnable coroutine is |
352 | or indirectly. The value 0 means that the only runnable coroutine is |
338 | the currently running one, so "cede" would have no effect, and |
353 | the currently running one, so "cede" would have no effect, and |
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365 | while the original code ref will be called (with parameters) from |
380 | while the original code ref will be called (with parameters) from |
366 | within another coroutine. |
381 | within another coroutine. |
367 | |
382 | |
368 | The reason this function exists is that many event libraries (such |
383 | The reason this function exists is that many event libraries (such |
369 | as the venerable Event module) are not coroutine-safe (a weaker form |
384 | as the venerable Event module) are not coroutine-safe (a weaker form |
370 | of thread-safety). This means you must not block within event |
385 | of reentrancy). This means you must not block within event |
371 | callbacks, otherwise you might suffer from crashes or worse. The |
386 | callbacks, otherwise you might suffer from crashes or worse. The |
372 | only event library currently known that is safe to use without |
387 | only event library currently known that is safe to use without |
373 | "unblock_sub" is EV. |
388 | "unblock_sub" is EV. |
374 | |
389 | |
375 | This function allows your callbacks to block by executing them in |
390 | This function allows your callbacks to block by executing them in |
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391 | some event callback, then you must not block either, or use |
406 | some event callback, then you must not block either, or use |
392 | "unblock_sub". |
407 | "unblock_sub". |
393 | |
408 | |
394 | $cb = Coro::rouse_cb |
409 | $cb = Coro::rouse_cb |
395 | Create and return a "rouse callback". That's a code reference that, |
410 | Create and return a "rouse callback". That's a code reference that, |
396 | when called, will save its arguments and notify the owner coroutine |
411 | when called, will remember a copy of its arguments and notify the |
397 | of the callback. |
412 | owner coroutine of the callback. |
398 | |
413 | |
399 | See the next function. |
414 | See the next function. |
400 | |
415 | |
401 | @args = Coro::rouse_wait [$cb] |
416 | @args = Coro::rouse_wait [$cb] |
402 | Wait for the specified rouse callback (or the last one tht was |
417 | Wait for the specified rouse callback (or the last one that was |
403 | created in this coroutine). |
418 | created in this coroutine). |
404 | |
419 | |
405 | As soon as the callback is invoked (or when the calback was invoked |
420 | As soon as the callback is invoked (or when the callback was invoked |
406 | before "rouse_wait"), it will return a copy of the arguments |
421 | before "rouse_wait"), it will return the arguments originally passed |
407 | originally passed to the rouse callback. |
422 | to the rouse callback. |
408 | |
423 | |
409 | See the section HOW TO WAIT FOR A CALLBACK for an actual usage |
424 | See the section HOW TO WAIT FOR A CALLBACK for an actual usage |
410 | example. |
425 | example. |
411 | |
426 | |
412 | HOW TO WAIT FOR A CALLBACK |
427 | HOW TO WAIT FOR A CALLBACK |
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429 | |
444 | |
430 | Coro offers two functions specifically designed to make this easy, |
445 | Coro offers two functions specifically designed to make this easy, |
431 | "Coro::rouse_cb" and "Coro::rouse_wait". |
446 | "Coro::rouse_cb" and "Coro::rouse_wait". |
432 | |
447 | |
433 | The first function, "rouse_cb", generates and returns a callback that, |
448 | The first function, "rouse_cb", generates and returns a callback that, |
434 | when invoked, will save it's arguments and notify the coroutine that |
449 | when invoked, will save its arguments and notify the coroutine that |
435 | created the callback. |
450 | created the callback. |
436 | |
451 | |
437 | The second function, "rouse_wait", waits for the callback to be called |
452 | The second function, "rouse_wait", waits for the callback to be called |
438 | (by calling "schedule" to go to sleep) and returns the arguments |
453 | (by calling "schedule" to go to sleep) and returns the arguments |
439 | originally passed to the callback. |
454 | originally passed to the callback. |
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480 | broken), then coroutines will not survive a fork. There is no known |
495 | broken), then coroutines will not survive a fork. There is no known |
481 | workaround except to fix your libc and use a saner backend. |
496 | workaround except to fix your libc and use a saner backend. |
482 | |
497 | |
483 | perl process emulation ("threads") |
498 | perl process emulation ("threads") |
484 | This module is not perl-pseudo-thread-safe. You should only ever use |
499 | This module is not perl-pseudo-thread-safe. You should only ever use |
485 | this module from the same thread (this requirement might be removed |
500 | this module from the first thread (this requirement might be removed |
486 | in the future to allow per-thread schedulers, but Coro::State does |
501 | in the future to allow per-thread schedulers, but Coro::State does |
487 | not yet allow this). I recommend disabling thread support and using |
502 | not yet allow this). I recommend disabling thread support and using |
488 | processes, as having the windows process emulation enabled under |
503 | processes, as having the windows process emulation enabled under |
489 | unix roughly halves perl performance, even when not used. |
504 | unix roughly halves perl performance, even when not used. |
490 | |
505 | |
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503 | |
518 | |
504 | Debugging: Coro::Debug. |
519 | Debugging: Coro::Debug. |
505 | |
520 | |
506 | Support/Utility: Coro::Specific, Coro::Util. |
521 | Support/Utility: Coro::Specific, Coro::Util. |
507 | |
522 | |
508 | Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
523 | Locking and IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
509 | Coro::SemaphoreSet, Coro::RWLock. |
524 | Coro::SemaphoreSet, Coro::RWLock. |
510 | |
525 | |
511 | IO/Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO. |
526 | I/O and Timers: Coro::Timer, Coro::Handle, Coro::Socket, Coro::AIO. |
512 | |
527 | |
513 | Compatibility: Coro::LWP, Coro::BDB, Coro::Storable, Coro::Select. |
528 | Compatibility with other modules: Coro::LWP (but see also AnyEvent::HTTP |
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529 | for a better-working alternative), Coro::BDB, Coro::Storable, |
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530 | Coro::Select. |
514 | |
531 | |
515 | XS API: Coro::MakeMaker. |
532 | XS API: Coro::MakeMaker. |
516 | |
533 | |
517 | Low level Configuration, Coroutine Environment: Coro::State. |
534 | Low level Configuration, Thread Environment, Continuations: Coro::State. |
518 | |
535 | |
519 | AUTHOR |
536 | AUTHOR |
520 | Marc Lehmann <schmorp@schmorp.de> |
537 | Marc Lehmann <schmorp@schmorp.de> |
521 | http://home.schmorp.de/ |
538 | http://home.schmorp.de/ |
522 | |
539 | |