1 | NAME |
1 | NAME |
2 | Coro - the only real threads in perl |
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; |
19 | use Coro::Semaphore; |
20 | my $lock = new Coro::Semaphore; |
20 | my $lock = new Coro::Semaphore; |
21 | my $locked; |
21 | my $locked; |
22 | |
22 | |
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 | For a tutorial-style introduction, please read the Coro::Intro manpage. |
28 | For a tutorial-style introduction, please read the Coro::Intro manpage. |
29 | This manpage mainly contains reference information. |
29 | This manpage mainly contains reference information. |
30 | |
30 | |
31 | This module collection manages continuations in general, most often in |
31 | This module collection manages continuations in general, most often in |
32 | the form of cooperative threads (also called coroutines in the |
32 | the form of cooperative threads (also called coros, or simply "coro" in |
33 | documentation). They are similar to kernel threads but don't (in |
33 | the documentation). They are similar to kernel threads but don't (in |
34 | general) run in parallel at the same time even on SMP machines. The |
34 | general) run in parallel at the same time even on SMP machines. The |
35 | specific flavor of thread offered by this module also guarantees you |
35 | specific flavor of thread offered by this module also guarantees you |
36 | that it will not switch between threads unless necessary, at |
36 | that it will not switch between threads unless necessary, at |
37 | easily-identified points in your program, so locking and parallel access |
37 | easily-identified points in your program, so locking and parallel access |
38 | are rarely an issue, making thread programming much safer and easier |
38 | are rarely an issue, making thread programming much safer and easier |
39 | than using other thread models. |
39 | than using other thread models. |
40 | |
40 | |
41 | Unlike the so-called "Perl threads" (which are not actually real threads |
41 | Unlike the so-called "Perl threads" (which are not actually real threads |
42 | but only the windows process emulation ported to unix), Coro provides a |
42 | but only the windows process emulation ported to unix, and as such act |
43 | full shared address space, which makes communication between threads |
43 | as processes), Coro provides a full shared address space, which makes |
44 | very easy. And threads are fast, too: disabling the Windows process |
44 | communication between threads very easy. And Coro's threads are fast, |
45 | emulation code in your perl and using Coro can easily result in a two to |
45 | too: disabling the Windows process emulation code in your perl and using |
46 | four times speed increase for your programs. |
46 | Coro can easily result in a two to four times speed increase for your |
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47 | programs. A parallel matrix multiplication benchmark runs over 300 times |
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48 | faster on a single core than perl's pseudo-threads on a quad core using |
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49 | all four cores. |
47 | |
50 | |
48 | Coro achieves that by supporting multiple running interpreters that |
51 | Coro achieves that by supporting multiple running interpreters that |
49 | share data, which is especially useful to code pseudo-parallel processes |
52 | share data, which is especially useful to code pseudo-parallel processes |
50 | and for event-based programming, such as multiple HTTP-GET requests |
53 | and for event-based programming, such as multiple HTTP-GET requests |
51 | running concurrently. See Coro::AnyEvent to learn more on how to |
54 | running concurrently. See Coro::AnyEvent to learn more on how to |
52 | integrate Coro into an event-based environment. |
55 | integrate Coro into an event-based environment. |
53 | |
56 | |
54 | In this module, a thread is defined as "callchain + lexical variables + |
57 | In this module, a thread is defined as "callchain + lexical variables + |
55 | @_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain, |
58 | some package variables + C stack), that is, a thread has its own |
56 | its own set of lexicals and its own set of perls most important global |
59 | callchain, its own set of lexicals and its own set of perls most |
57 | variables (see Coro::State for more configuration and background info). |
60 | important global variables (see Coro::State for more configuration and |
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61 | background info). |
58 | |
62 | |
59 | See also the "SEE ALSO" section at the end of this document - the Coro |
63 | See also the "SEE ALSO" section at the end of this document - the Coro |
60 | module family is quite large. |
64 | module family is quite large. |
61 | |
65 | |
62 | GLOBAL VARIABLES |
66 | GLOBAL VARIABLES |
63 | $Coro::main |
67 | $Coro::main |
64 | This variable stores the coroutine object that represents the main |
68 | This variable stores the Coro object that represents the main |
65 | program. While you cna "ready" it and do most other things you can |
69 | program. While you cna "ready" it and do most other things you can |
66 | do to coroutines, it is mainly useful to compare again |
70 | do to coro, it is mainly useful to compare again $Coro::current, to |
67 | $Coro::current, to see whether you are running in the main program |
71 | see whether you are running in the main program or not. |
68 | or not. |
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69 | |
72 | |
70 | $Coro::current |
73 | $Coro::current |
71 | The coroutine object representing the current coroutine (the last |
74 | The Coro object representing the current coro (the last coro that |
72 | coroutine that the Coro scheduler switched to). The initial value is |
75 | the Coro scheduler switched to). The initial value is $Coro::main |
73 | $Coro::main (of course). |
76 | (of course). |
74 | |
77 | |
75 | This variable is strictly *read-only*. You can take copies of the |
78 | This variable is strictly *read-only*. You can take copies of the |
76 | value stored in it and use it as any other coroutine object, but you |
79 | value stored in it and use it as any other Coro object, but you must |
77 | must not otherwise modify the variable itself. |
80 | not otherwise modify the variable itself. |
78 | |
81 | |
79 | $Coro::idle |
82 | $Coro::idle |
80 | This variable is mainly useful to integrate Coro into event loops. |
83 | This variable is mainly useful to integrate Coro into event loops. |
81 | It is usually better to rely on Coro::AnyEvent or Coro::EV, as this |
84 | It is usually better to rely on Coro::AnyEvent or Coro::EV, as this |
82 | is pretty low-level functionality. |
85 | is pretty low-level functionality. |
83 | |
86 | |
84 | This variable stores either a coroutine or a callback. |
87 | This variable stores either a Coro object or a callback. |
85 | |
88 | |
86 | If it is a callback, the it is called whenever the scheduler finds |
89 | If it is a callback, the it is called whenever the scheduler finds |
87 | no ready coroutines to run. The default implementation prints |
90 | no ready coros to run. The default implementation prints "FATAL: |
88 | "FATAL: deadlock detected" and exits, because the program has no |
91 | deadlock detected" and exits, because the program has no other way |
89 | other way to continue. |
92 | to continue. |
90 | |
93 | |
91 | If it is a coroutine object, then this object will be readied |
94 | If it is a coro object, then this object will be readied (without |
92 | (without invoking any ready hooks, however) when the scheduler finds |
95 | invoking any ready hooks, however) when the scheduler finds no other |
93 | no other ready coroutines to run. |
96 | ready coros to run. |
94 | |
97 | |
95 | This hook is overwritten by modules such as "Coro::EV" and |
98 | This hook is overwritten by modules such as "Coro::EV" and |
96 | "Coro::AnyEvent" to wait on an external event that hopefully wake up |
99 | "Coro::AnyEvent" to wait on an external event that hopefully wake up |
97 | a coroutine so the scheduler can run it. |
100 | a coro so the scheduler can run it. |
98 | |
101 | |
99 | Note that the callback *must not*, under any circumstances, block |
102 | Note that the callback *must not*, under any circumstances, block |
100 | the current coroutine. Normally, this is achieved by having an "idle |
103 | the current coro. Normally, this is achieved by having an "idle |
101 | coroutine" that calls the event loop and then blocks again, and then |
104 | coro" that calls the event loop and then blocks again, and then |
102 | readying that coroutine in the idle handler, or by simply placing |
105 | readying that coro in the idle handler, or by simply placing the |
103 | the idle coroutine in this variable. |
106 | idle coro in this variable. |
104 | |
107 | |
105 | See Coro::Event or Coro::AnyEvent for examples of using this |
108 | See Coro::Event or Coro::AnyEvent for examples of using this |
106 | technique. |
109 | technique. |
107 | |
110 | |
108 | Please note that if your callback recursively invokes perl (e.g. for |
111 | Please note that if your callback recursively invokes perl (e.g. for |
109 | event handlers), then it must be prepared to be called recursively |
112 | event handlers), then it must be prepared to be called recursively |
110 | itself. |
113 | itself. |
111 | |
114 | |
112 | SIMPLE COROUTINE CREATION |
115 | SIMPLE CORO CREATION |
113 | async { ... } [@args...] |
116 | async { ... } [@args...] |
114 | Create a new coroutine and return its coroutine object (usually |
117 | Create a new coro and return its Coro object (usually unused). The |
115 | unused). The coroutine will be put into the ready queue, so it will |
118 | coro will be put into the ready queue, so it will start running |
116 | start running automatically on the next scheduler run. |
119 | automatically on the next scheduler run. |
117 | |
120 | |
118 | The first argument is a codeblock/closure that should be executed in |
121 | The first argument is a codeblock/closure that should be executed in |
119 | the coroutine. When it returns argument returns the coroutine is |
122 | the coro. When it returns argument returns the coro is automatically |
120 | automatically terminated. |
123 | terminated. |
121 | |
124 | |
122 | The remaining arguments are passed as arguments to the closure. |
125 | The remaining arguments are passed as arguments to the closure. |
123 | |
126 | |
124 | See the "Coro::State::new" constructor for info about the coroutine |
127 | See the "Coro::State::new" constructor for info about the coro |
125 | environment in which coroutines are executed. |
128 | environment in which coro are executed. |
126 | |
129 | |
127 | Calling "exit" in a coroutine will do the same as calling exit |
130 | Calling "exit" in a coro will do the same as calling exit outside |
128 | outside the coroutine. Likewise, when the coroutine dies, the |
131 | the coro. Likewise, when the coro dies, the program will exit, just |
129 | program will exit, just as it would in the main program. |
132 | as it would in the main program. |
130 | |
133 | |
131 | If you do not want that, you can provide a default "die" handler, or |
134 | If you do not want that, you can provide a default "die" handler, or |
132 | simply avoid dieing (by use of "eval"). |
135 | simply avoid dieing (by use of "eval"). |
133 | |
136 | |
134 | Example: Create a new coroutine that just prints its arguments. |
137 | Example: Create a new coro that just prints its arguments. |
135 | |
138 | |
136 | async { |
139 | async { |
137 | print "@_\n"; |
140 | print "@_\n"; |
138 | } 1,2,3,4; |
141 | } 1,2,3,4; |
139 | |
142 | |
140 | async_pool { ... } [@args...] |
143 | async_pool { ... } [@args...] |
141 | Similar to "async", but uses a coroutine pool, so you should not |
144 | Similar to "async", but uses a coro pool, so you should not call |
142 | call terminate or join on it (although you are allowed to), and you |
145 | terminate or join on it (although you are allowed to), and you get a |
143 | get a coroutine that might have executed other code already (which |
146 | coro that might have executed other code already (which can be good |
144 | can be good or bad :). |
147 | or bad :). |
145 | |
148 | |
146 | On the plus side, this function is about twice as fast as creating |
149 | On the plus side, this function is about twice as fast as creating |
147 | (and destroying) a completely new coroutine, so if you need a lot of |
150 | (and destroying) a completely new coro, so if you need a lot of |
148 | generic coroutines in quick successsion, use "async_pool", not |
151 | generic coros in quick successsion, use "async_pool", not "async". |
149 | "async". |
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150 | |
152 | |
151 | The code block is executed in an "eval" context and a warning will |
153 | The code block is executed in an "eval" context and a warning will |
152 | be issued in case of an exception instead of terminating the |
154 | be issued in case of an exception instead of terminating the |
153 | program, as "async" does. As the coroutine is being reused, stuff |
155 | program, as "async" does. As the coro is being reused, stuff like |
154 | like "on_destroy" will not work in the expected way, unless you call |
156 | "on_destroy" will not work in the expected way, unless you call |
155 | terminate or cancel, which somehow defeats the purpose of pooling |
157 | terminate or cancel, which somehow defeats the purpose of pooling |
156 | (but is fine in the exceptional case). |
158 | (but is fine in the exceptional case). |
157 | |
159 | |
158 | The priority will be reset to 0 after each run, tracing will be |
160 | The priority will be reset to 0 after each run, tracing will be |
159 | disabled, the description will be reset and the default output |
161 | disabled, the description will be reset and the default output |
160 | filehandle gets restored, so you can change all these. Otherwise the |
162 | filehandle gets restored, so you can change all these. Otherwise the |
161 | coroutine will be re-used "as-is": most notably if you change other |
163 | coro will be re-used "as-is": most notably if you change other |
162 | per-coroutine global stuff such as $/ you *must needs* revert that |
164 | per-coro global stuff such as $/ you *must needs* revert that |
163 | change, which is most simply done by using local as in: "local $/". |
165 | change, which is most simply done by using local as in: "local $/". |
164 | |
166 | |
165 | The idle pool size is limited to 8 idle coroutines (this can be |
167 | The idle pool size is limited to 8 idle coros (this can be adjusted |
166 | adjusted by changing $Coro::POOL_SIZE), but there can be as many |
168 | by changing $Coro::POOL_SIZE), but there can be as many non-idle |
167 | non-idle coros as required. |
169 | coros as required. |
168 | |
170 | |
169 | If you are concerned about pooled coroutines growing a lot because a |
171 | If you are concerned about pooled coros growing a lot because a |
170 | single "async_pool" used a lot of stackspace you can e.g. |
172 | single "async_pool" used a lot of stackspace you can e.g. |
171 | "async_pool { terminate }" once per second or so to slowly replenish |
173 | "async_pool { terminate }" once per second or so to slowly replenish |
172 | the pool. In addition to that, when the stacks used by a handler |
174 | the pool. In addition to that, when the stacks used by a handler |
173 | grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also |
175 | grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also |
174 | be destroyed. |
176 | be destroyed. |
175 | |
177 | |
176 | STATIC METHODS |
178 | STATIC METHODS |
177 | Static methods are actually functions that implicitly operate on the |
179 | Static methods are actually functions that implicitly operate on the |
178 | current coroutine. |
180 | current coro. |
179 | |
181 | |
180 | schedule |
182 | schedule |
181 | Calls the scheduler. The scheduler will find the next coroutine that |
183 | Calls the scheduler. The scheduler will find the next coro that is |
182 | is to be run from the ready queue and switches to it. The next |
184 | to be run from the ready queue and switches to it. The next coro to |
183 | coroutine to be run is simply the one with the highest priority that |
185 | be run is simply the one with the highest priority that is longest |
184 | is longest in its ready queue. If there is no coroutine ready, it |
186 | in its ready queue. If there is no coro ready, it will clal the |
185 | will clal the $Coro::idle hook. |
187 | $Coro::idle hook. |
186 | |
188 | |
187 | Please note that the current coroutine will *not* be put into the |
189 | Please note that the current coro will *not* be put into the ready |
188 | ready queue, so calling this function usually means you will never |
190 | queue, so calling this function usually means you will never be |
189 | be called again unless something else (e.g. an event handler) calls |
191 | called again unless something else (e.g. an event handler) calls |
190 | "->ready", thus waking you up. |
192 | "->ready", thus waking you up. |
191 | |
193 | |
192 | This makes "schedule" *the* generic method to use to block the |
194 | This makes "schedule" *the* generic method to use to block the |
193 | current coroutine and wait for events: first you remember the |
195 | current coro and wait for events: first you remember the current |
194 | current coroutine in a variable, then arrange for some callback of |
196 | coro in a variable, then arrange for some callback of yours to call |
195 | yours to call "->ready" on that once some event happens, and last |
197 | "->ready" on that once some event happens, and last you call |
196 | you call "schedule" to put yourself to sleep. Note that a lot of |
198 | "schedule" to put yourself to sleep. Note that a lot of things can |
197 | things can wake your coroutine up, so you need to check whether the |
199 | wake your coro up, so you need to check whether the event indeed |
198 | event indeed happened, e.g. by storing the status in a variable. |
200 | happened, e.g. by storing the status in a variable. |
199 | |
201 | |
200 | See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for |
202 | See HOW TO WAIT FOR A CALLBACK, below, for some ways to wait for |
201 | callbacks. |
203 | callbacks. |
202 | |
204 | |
203 | cede |
205 | cede |
204 | "Cede" to other coroutines. This function puts the current coroutine |
206 | "Cede" to other coros. This function puts the current coro into the |
205 | into the ready queue and calls "schedule", which has the effect of |
207 | ready queue and calls "schedule", which has the effect of giving up |
206 | giving up the current "timeslice" to other coroutines of the same or |
208 | the current "timeslice" to other coros of the same or higher |
207 | higher priority. Once your coroutine gets its turn again it will |
209 | priority. Once your coro gets its turn again it will automatically |
208 | automatically be resumed. |
210 | be resumed. |
209 | |
211 | |
210 | This function is often called "yield" in other languages. |
212 | This function is often called "yield" in other languages. |
211 | |
213 | |
212 | Coro::cede_notself |
214 | Coro::cede_notself |
213 | Works like cede, but is not exported by default and will cede to |
215 | Works like cede, but is not exported by default and will cede to |
214 | *any* coroutine, regardless of priority. This is useful sometimes to |
216 | *any* coro, regardless of priority. This is useful sometimes to |
215 | ensure progress is made. |
217 | ensure progress is made. |
216 | |
218 | |
217 | terminate [arg...] |
219 | terminate [arg...] |
218 | Terminates the current coroutine with the given status values (see |
220 | Terminates the current coro with the given status values (see |
219 | cancel). |
221 | cancel). |
220 | |
222 | |
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223 | Coro::on_enter BLOCK, Coro::on_leave BLOCK |
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224 | These function install enter and leave winders in the current scope. |
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225 | The enter block will be executed when on_enter is called and |
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226 | whenever the current coro is re-entered by the scheduler, while the |
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227 | leave block is executed whenever the current coro is blocked by the |
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228 | scheduler, and also when the containing scope is exited (by whatever |
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229 | means, be it exit, die, last etc.). |
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230 | |
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231 | *Neither invoking the scheduler, nor exceptions, are allowed within |
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232 | those BLOCKs*. That means: do not even think about calling "die" |
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233 | without an eval, and do not even think of entering the scheduler in |
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234 | any way. |
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235 | |
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236 | Since both BLOCKs are tied to the current scope, they will |
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237 | automatically be removed when the current scope exits. |
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238 | |
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239 | These functions implement the same concept as "dynamic-wind" in |
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240 | scheme does, and are useful when you want to localise some resource |
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241 | to a specific coro. |
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242 | |
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243 | They slow down thread switching considerably for coros that use them |
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244 | (about 40% for a BLOCK with a single assignment, so thread switching |
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245 | is still reasonably fast if the handlers are fast). |
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246 | |
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247 | These functions are best understood by an example: The following |
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248 | function will change the current timezone to |
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249 | "Antarctica/South_Pole", which requires a call to "tzset", but by |
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250 | using "on_enter" and "on_leave", which remember/change the current |
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251 | timezone and restore the previous value, respectively, the timezone |
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252 | is only changed for the coro that installed those handlers. |
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253 | |
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254 | use POSIX qw(tzset); |
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255 | |
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256 | async { |
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257 | my $old_tz; # store outside TZ value here |
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258 | |
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259 | Coro::on_enter { |
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260 | $old_tz = $ENV{TZ}; # remember the old value |
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261 | |
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262 | $ENV{TZ} = "Antarctica/South_Pole"; |
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263 | tzset; # enable new value |
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264 | }; |
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265 | |
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266 | Coro::on_leave { |
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267 | $ENV{TZ} = $old_tz; |
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268 | tzset; # restore old value |
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269 | }; |
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270 | |
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271 | # at this place, the timezone is Antarctica/South_Pole, |
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272 | # without disturbing the TZ of any other coro. |
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273 | }; |
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274 | |
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275 | This can be used to localise about any resource (locale, uid, |
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276 | current working directory etc.) to a block, despite the existance of |
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277 | other coros. |
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278 | |
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279 | Another interesting example implements time-sliced multitasking |
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280 | using interval timers (this could obviously be optimised, but does |
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281 | the job): |
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282 | |
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283 | # "timeslice" the given block |
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284 | sub timeslice(&) { |
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285 | use Time::HiRes (); |
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286 | |
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287 | Coro::on_enter { |
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288 | # on entering the thread, we set an VTALRM handler to cede |
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289 | $SIG{VTALRM} = sub { cede }; |
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290 | # and then start the interval timer |
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291 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
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292 | }; |
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293 | Coro::on_leave { |
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294 | # on leaving the thread, we stop the interval timer again |
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295 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
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296 | }; |
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297 | |
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298 | &{+shift}; |
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299 | } |
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300 | |
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301 | # use like this: |
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302 | timeslice { |
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303 | # The following is an endless loop that would normally |
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304 | # monopolise the process. Since it runs in a timesliced |
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305 | # environment, it will regularly cede to other threads. |
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306 | while () { } |
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307 | }; |
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308 | |
221 | killall |
309 | killall |
222 | Kills/terminates/cancels all coroutines except the currently running |
310 | Kills/terminates/cancels all coros except the currently running one. |
223 | one. This is useful after a fork, either in the child or the parent, |
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224 | as usually only one of them should inherit the running coroutines. |
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225 | |
311 | |
226 | Note that while this will try to free some of the main programs |
312 | Note that while this will try to free some of the main interpreter |
227 | resources, you cannot free all of them, so if a coroutine that is |
313 | resources if the calling coro isn't the main coro, but one cannot |
228 | not the main program calls this function, there will be some |
314 | free all of them, so if a coro that is not the main coro calls this |
229 | one-time resource leak. |
315 | function, there will be some one-time resource leak. |
230 | |
316 | |
231 | COROUTINE OBJECT METHODS |
317 | CORO OBJECT METHODS |
232 | These are the methods you can call on coroutine objects (or to create |
318 | These are the methods you can call on coro objects (or to create them). |
233 | them). |
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234 | |
319 | |
235 | new Coro \&sub [, @args...] |
320 | new Coro \&sub [, @args...] |
236 | Create a new coroutine and return it. When the sub returns, the |
321 | Create a new coro and return it. When the sub returns, the coro |
237 | coroutine automatically terminates as if "terminate" with the |
322 | automatically terminates as if "terminate" with the returned values |
238 | returned values were called. To make the coroutine run you must |
323 | were called. To make the coro run you must first put it into the |
239 | first put it into the ready queue by calling the ready method. |
324 | ready queue by calling the ready method. |
240 | |
325 | |
241 | See "async" and "Coro::State::new" for additional info about the |
326 | See "async" and "Coro::State::new" for additional info about the |
242 | coroutine environment. |
327 | coro environment. |
243 | |
328 | |
244 | $success = $coroutine->ready |
329 | $success = $coro->ready |
245 | Put the given coroutine into the end of its ready queue (there is |
330 | Put the given coro into the end of its ready queue (there is one |
246 | one queue for each priority) and return true. If the coroutine is |
331 | queue for each priority) and return true. If the coro is already in |
247 | already in the ready queue, do nothing and return false. |
332 | the ready queue, do nothing and return false. |
248 | |
333 | |
249 | This ensures that the scheduler will resume this coroutine |
334 | This ensures that the scheduler will resume this coro automatically |
250 | automatically once all the coroutines of higher priority and all |
335 | once all the coro of higher priority and all coro of the same |
251 | coroutines of the same priority that were put into the ready queue |
336 | priority that were put into the ready queue earlier have been |
252 | earlier have been resumed. |
337 | resumed. |
253 | |
338 | |
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339 | $coro->suspend |
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340 | Suspends the specified coro. A suspended coro works just like any |
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341 | other coro, except that the scheduler will not select a suspended |
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342 | coro for execution. |
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343 | |
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344 | Suspending a coro can be useful when you want to keep the coro from |
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345 | running, but you don't want to destroy it, or when you want to |
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346 | temporarily freeze a coro (e.g. for debugging) to resume it later. |
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347 | |
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348 | A scenario for the former would be to suspend all (other) coros |
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349 | after a fork and keep them alive, so their destructors aren't |
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350 | called, but new coros can be created. |
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351 | |
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352 | $coro->resume |
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353 | If the specified coro was suspended, it will be resumed. Note that |
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354 | when the coro was in the ready queue when it was suspended, it might |
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355 | have been unreadied by the scheduler, so an activation might have |
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356 | been lost. |
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357 | |
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358 | To avoid this, it is best to put a suspended coro into the ready |
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359 | queue unconditionally, as every synchronisation mechanism must |
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360 | protect itself against spurious wakeups, and the one in the Coro |
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361 | family certainly do that. |
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362 | |
254 | $is_ready = $coroutine->is_ready |
363 | $is_ready = $coro->is_ready |
255 | Return whether the coroutine is currently the ready queue or not, |
364 | Returns true iff the Coro object is in the ready queue. Unless the |
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365 | Coro object gets destroyed, it will eventually be scheduled by the |
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366 | scheduler. |
256 | |
367 | |
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368 | $is_running = $coro->is_running |
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369 | Returns true iff the Coro object is currently running. Only one Coro |
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370 | object can ever be in the running state (but it currently is |
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371 | possible to have multiple running Coro::States). |
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372 | |
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373 | $is_suspended = $coro->is_suspended |
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374 | Returns true iff this Coro object has been suspended. Suspended |
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375 | Coros will not ever be scheduled. |
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376 | |
257 | $coroutine->cancel (arg...) |
377 | $coro->cancel (arg...) |
258 | Terminates the given coroutine and makes it return the given |
378 | Terminates the given Coro and makes it return the given arguments as |
259 | arguments as status (default: the empty list). Never returns if the |
379 | status (default: the empty list). Never returns if the Coro is the |
260 | coroutine is the current coroutine. |
380 | current Coro. |
261 | |
381 | |
262 | $coroutine->schedule_to |
382 | $coro->schedule_to |
263 | Puts the current coroutine to sleep (like "Coro::schedule"), but |
383 | Puts the current coro to sleep (like "Coro::schedule"), but instead |
264 | instead of continuing with the next coro from the ready queue, |
384 | of continuing with the next coro from the ready queue, always switch |
265 | always switch to the given coroutine object (regardless of priority |
385 | to the given coro object (regardless of priority etc.). The |
266 | etc.). The readyness state of that coroutine isn't changed. |
386 | readyness state of that coro isn't changed. |
267 | |
387 | |
268 | This is an advanced method for special cases - I'd love to hear |
388 | This is an advanced method for special cases - I'd love to hear |
269 | about any uses for this one. |
389 | about any uses for this one. |
270 | |
390 | |
271 | $coroutine->cede_to |
391 | $coro->cede_to |
272 | Like "schedule_to", but puts the current coroutine into the ready |
392 | Like "schedule_to", but puts the current coro into the ready queue. |
273 | queue. This has the effect of temporarily switching to the given |
393 | This has the effect of temporarily switching to the given coro, and |
274 | coroutine, and continuing some time later. |
394 | continuing some time later. |
275 | |
395 | |
276 | This is an advanced method for special cases - I'd love to hear |
396 | This is an advanced method for special cases - I'd love to hear |
277 | about any uses for this one. |
397 | about any uses for this one. |
278 | |
398 | |
279 | $coroutine->throw ([$scalar]) |
399 | $coro->throw ([$scalar]) |
280 | If $throw is specified and defined, it will be thrown as an |
400 | If $throw is specified and defined, it will be thrown as an |
281 | exception inside the coroutine at the next convenient point in time. |
401 | exception inside the coro at the next convenient point in time. |
282 | Otherwise clears the exception object. |
402 | Otherwise clears the exception object. |
283 | |
403 | |
284 | Coro will check for the exception each time a schedule-like-function |
404 | Coro will check for the exception each time a schedule-like-function |
285 | returns, i.e. after each "schedule", "cede", |
405 | returns, i.e. after each "schedule", "cede", |
286 | "Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of |
406 | "Coro::Semaphore->down", "Coro::Handle->readable" and so on. Most of |
… | |
… | |
289 | |
409 | |
290 | The exception object will be thrown "as is" with the specified |
410 | The exception object will be thrown "as is" with the specified |
291 | scalar in $@, i.e. if it is a string, no line number or newline will |
411 | scalar in $@, i.e. if it is a string, no line number or newline will |
292 | be appended (unlike with "die"). |
412 | be appended (unlike with "die"). |
293 | |
413 | |
294 | This can be used as a softer means than "cancel" to ask a coroutine |
414 | This can be used as a softer means than "cancel" to ask a coro to |
295 | to end itself, although there is no guarantee that the exception |
415 | end itself, although there is no guarantee that the exception will |
296 | will lead to termination, and if the exception isn't caught it might |
416 | lead to termination, and if the exception isn't caught it might well |
297 | well end the whole program. |
417 | end the whole program. |
298 | |
418 | |
299 | You might also think of "throw" as being the moral equivalent of |
419 | You might also think of "throw" as being the moral equivalent of |
300 | "kill"ing a coroutine with a signal (in this case, a scalar). |
420 | "kill"ing a coro with a signal (in this case, a scalar). |
301 | |
421 | |
302 | $coroutine->join |
422 | $coro->join |
303 | Wait until the coroutine terminates and return any values given to |
423 | Wait until the coro terminates and return any values given to the |
304 | the "terminate" or "cancel" functions. "join" can be called |
424 | "terminate" or "cancel" functions. "join" can be called concurrently |
305 | concurrently from multiple coroutines, and all will be resumed and |
425 | from multiple coro, and all will be resumed and given the status |
306 | given the status return once the $coroutine terminates. |
426 | return once the $coro terminates. |
307 | |
427 | |
308 | $coroutine->on_destroy (\&cb) |
428 | $coro->on_destroy (\&cb) |
309 | Registers a callback that is called when this coroutine gets |
429 | Registers a callback that is called when this coro gets destroyed, |
310 | destroyed, but before it is joined. The callback gets passed the |
430 | but before it is joined. The callback gets passed the terminate |
311 | terminate arguments, if any, and *must not* die, under any |
431 | arguments, if any, and *must not* die, under any circumstances. |
312 | circumstances. |
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313 | |
432 | |
314 | $oldprio = $coroutine->prio ($newprio) |
433 | $oldprio = $coro->prio ($newprio) |
315 | Sets (or gets, if the argument is missing) the priority of the |
434 | Sets (or gets, if the argument is missing) the priority of the coro. |
316 | coroutine. Higher priority coroutines get run before lower priority |
435 | Higher priority coro get run before lower priority coro. Priorities |
317 | coroutines. Priorities are small signed integers (currently -4 .. |
436 | are small signed integers (currently -4 .. +3), that you can refer |
318 | +3), that you can refer to using PRIO_xxx constants (use the import |
437 | to using PRIO_xxx constants (use the import tag :prio to get then): |
319 | tag :prio to get then): |
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320 | |
438 | |
321 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
439 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
322 | 3 > 1 > 0 > -1 > -3 > -4 |
440 | 3 > 1 > 0 > -1 > -3 > -4 |
323 | |
441 | |
324 | # set priority to HIGH |
442 | # set priority to HIGH |
325 | current->prio(PRIO_HIGH); |
443 | current->prio (PRIO_HIGH); |
326 | |
444 | |
327 | The idle coroutine ($Coro::idle) always has a lower priority than |
445 | The idle coro ($Coro::idle) always has a lower priority than any |
328 | any existing coroutine. |
446 | existing coro. |
329 | |
447 | |
330 | Changing the priority of the current coroutine will take effect |
448 | Changing the priority of the current coro will take effect |
331 | immediately, but changing the priority of coroutines in the ready |
449 | immediately, but changing the priority of coro in the ready queue |
332 | queue (but not running) will only take effect after the next |
450 | (but not running) will only take effect after the next schedule (of |
333 | schedule (of that coroutine). This is a bug that will be fixed in |
451 | that coro). This is a bug that will be fixed in some future version. |
334 | some future version. |
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335 | |
452 | |
336 | $newprio = $coroutine->nice ($change) |
453 | $newprio = $coro->nice ($change) |
337 | Similar to "prio", but subtract the given value from the priority |
454 | Similar to "prio", but subtract the given value from the priority |
338 | (i.e. higher values mean lower priority, just as in unix). |
455 | (i.e. higher values mean lower priority, just as in unix). |
339 | |
456 | |
340 | $olddesc = $coroutine->desc ($newdesc) |
457 | $olddesc = $coro->desc ($newdesc) |
341 | Sets (or gets in case the argument is missing) the description for |
458 | Sets (or gets in case the argument is missing) the description for |
342 | this coroutine. This is just a free-form string you can associate |
459 | this coro. This is just a free-form string you can associate with a |
343 | with a coroutine. |
460 | coro. |
344 | |
461 | |
345 | This method simply sets the "$coroutine->{desc}" member to the given |
462 | This method simply sets the "$coro->{desc}" member to the given |
346 | string. You can modify this member directly if you wish. |
463 | string. You can modify this member directly if you wish. |
347 | |
464 | |
348 | GLOBAL FUNCTIONS |
465 | GLOBAL FUNCTIONS |
349 | Coro::nready |
466 | Coro::nready |
350 | Returns the number of coroutines that are currently in the ready |
467 | Returns the number of coro that are currently in the ready state, |
351 | state, i.e. that can be switched to by calling "schedule" directory |
468 | i.e. that can be switched to by calling "schedule" directory or |
352 | or indirectly. The value 0 means that the only runnable coroutine is |
469 | indirectly. The value 0 means that the only runnable coro is the |
353 | the currently running one, so "cede" would have no effect, and |
470 | currently running one, so "cede" would have no effect, and |
354 | "schedule" would cause a deadlock unless there is an idle handler |
471 | "schedule" would cause a deadlock unless there is an idle handler |
355 | that wakes up some coroutines. |
472 | that wakes up some coro. |
356 | |
473 | |
357 | my $guard = Coro::guard { ... } |
474 | my $guard = Coro::guard { ... } |
358 | This creates and returns a guard object. Nothing happens until the |
475 | This function still exists, but is deprecated. Please use the |
359 | object gets destroyed, in which case the codeblock given as argument |
476 | "Guard::guard" function instead. |
360 | will be executed. This is useful to free locks or other resources in |
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361 | case of a runtime error or when the coroutine gets canceled, as in |
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362 | both cases the guard block will be executed. The guard object |
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363 | supports only one method, "->cancel", which will keep the codeblock |
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364 | from being executed. |
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365 | |
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366 | Example: set some flag and clear it again when the coroutine gets |
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367 | canceled or the function returns: |
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368 | |
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369 | sub do_something { |
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370 | my $guard = Coro::guard { $busy = 0 }; |
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371 | $busy = 1; |
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372 | |
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373 | # do something that requires $busy to be true |
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374 | } |
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375 | |
477 | |
376 | unblock_sub { ... } |
478 | unblock_sub { ... } |
377 | This utility function takes a BLOCK or code reference and "unblocks" |
479 | This utility function takes a BLOCK or code reference and "unblocks" |
378 | it, returning a new coderef. Unblocking means that calling the new |
480 | it, returning a new coderef. Unblocking means that calling the new |
379 | coderef will return immediately without blocking, returning nothing, |
481 | coderef will return immediately without blocking, returning nothing, |
380 | while the original code ref will be called (with parameters) from |
482 | while the original code ref will be called (with parameters) from |
381 | within another coroutine. |
483 | within another coro. |
382 | |
484 | |
383 | The reason this function exists is that many event libraries (such |
485 | The reason this function exists is that many event libraries (such |
384 | as the venerable Event module) are not coroutine-safe (a weaker form |
486 | as the venerable Event module) are not thread-safe (a weaker form of |
385 | of reentrancy). This means you must not block within event |
487 | reentrancy). This means you must not block within event callbacks, |
386 | callbacks, otherwise you might suffer from crashes or worse. The |
488 | otherwise you might suffer from crashes or worse. The only event |
387 | only event library currently known that is safe to use without |
489 | library currently known that is safe to use without "unblock_sub" is |
388 | "unblock_sub" is EV. |
490 | EV. |
389 | |
491 | |
390 | This function allows your callbacks to block by executing them in |
492 | This function allows your callbacks to block by executing them in |
391 | another coroutine where it is safe to block. One example where |
493 | another coro where it is safe to block. One example where blocking |
392 | blocking is handy is when you use the Coro::AIO functions to save |
494 | is handy is when you use the Coro::AIO functions to save results to |
393 | results to disk, for example. |
495 | disk, for example. |
394 | |
496 | |
395 | In short: simply use "unblock_sub { ... }" instead of "sub { ... }" |
497 | In short: simply use "unblock_sub { ... }" instead of "sub { ... }" |
396 | when creating event callbacks that want to block. |
498 | when creating event callbacks that want to block. |
397 | |
499 | |
398 | If your handler does not plan to block (e.g. simply sends a message |
500 | If your handler does not plan to block (e.g. simply sends a message |
399 | to another coroutine, or puts some other coroutine into the ready |
501 | to another coro, or puts some other coro into the ready queue), |
400 | queue), there is no reason to use "unblock_sub". |
502 | there is no reason to use "unblock_sub". |
401 | |
503 | |
402 | Note that you also need to use "unblock_sub" for any other callbacks |
504 | Note that you also need to use "unblock_sub" for any other callbacks |
403 | that are indirectly executed by any C-based event loop. For example, |
505 | that are indirectly executed by any C-based event loop. For example, |
404 | when you use a module that uses AnyEvent (and you use |
506 | when you use a module that uses AnyEvent (and you use |
405 | Coro::AnyEvent) and it provides callbacks that are the result of |
507 | Coro::AnyEvent) and it provides callbacks that are the result of |
… | |
… | |
407 | "unblock_sub". |
509 | "unblock_sub". |
408 | |
510 | |
409 | $cb = Coro::rouse_cb |
511 | $cb = Coro::rouse_cb |
410 | Create and return a "rouse callback". That's a code reference that, |
512 | Create and return a "rouse callback". That's a code reference that, |
411 | when called, will remember a copy of its arguments and notify the |
513 | when called, will remember a copy of its arguments and notify the |
412 | owner coroutine of the callback. |
514 | owner coro of the callback. |
413 | |
515 | |
414 | See the next function. |
516 | See the next function. |
415 | |
517 | |
416 | @args = Coro::rouse_wait [$cb] |
518 | @args = Coro::rouse_wait [$cb] |
417 | Wait for the specified rouse callback (or the last one that was |
519 | Wait for the specified rouse callback (or the last one that was |
418 | created in this coroutine). |
520 | created in this coro). |
419 | |
521 | |
420 | As soon as the callback is invoked (or when the callback was invoked |
522 | As soon as the callback is invoked (or when the callback was invoked |
421 | before "rouse_wait"), it will return the arguments originally passed |
523 | before "rouse_wait"), it will return the arguments originally passed |
422 | to the rouse callback. |
524 | to the rouse callback. |
423 | |
525 | |
424 | See the section HOW TO WAIT FOR A CALLBACK for an actual usage |
526 | See the section HOW TO WAIT FOR A CALLBACK for an actual usage |
425 | example. |
527 | example. |
426 | |
528 | |
427 | HOW TO WAIT FOR A CALLBACK |
529 | HOW TO WAIT FOR A CALLBACK |
428 | It is very common for a coroutine to wait for some callback to be |
530 | It is very common for a coro to wait for some callback to be called. |
429 | called. This occurs naturally when you use coroutines in an otherwise |
531 | This occurs naturally when you use coro in an otherwise event-based |
430 | event-based program, or when you use event-based libraries. |
532 | program, or when you use event-based libraries. |
431 | |
533 | |
432 | These typically register a callback for some event, and call that |
534 | These typically register a callback for some event, and call that |
433 | callback when the event occured. In a coroutine, however, you typically |
535 | callback when the event occured. In a coro, however, you typically want |
434 | want to just wait for the event, simplyifying things. |
536 | to just wait for the event, simplyifying things. |
435 | |
537 | |
436 | For example "AnyEvent->child" registers a callback to be called when a |
538 | For example "AnyEvent->child" registers a callback to be called when a |
437 | specific child has exited: |
539 | specific child has exited: |
438 | |
540 | |
439 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
541 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
440 | |
542 | |
441 | But from withina coroutine, you often just want to write this: |
543 | But from within a coro, you often just want to write this: |
442 | |
544 | |
443 | my $status = wait_for_child $pid; |
545 | my $status = wait_for_child $pid; |
444 | |
546 | |
445 | Coro offers two functions specifically designed to make this easy, |
547 | Coro offers two functions specifically designed to make this easy, |
446 | "Coro::rouse_cb" and "Coro::rouse_wait". |
548 | "Coro::rouse_cb" and "Coro::rouse_wait". |
447 | |
549 | |
448 | The first function, "rouse_cb", generates and returns a callback that, |
550 | The first function, "rouse_cb", generates and returns a callback that, |
449 | when invoked, will save its arguments and notify the coroutine that |
551 | when invoked, will save its arguments and notify the coro that created |
450 | created the callback. |
552 | the callback. |
451 | |
553 | |
452 | The second function, "rouse_wait", waits for the callback to be called |
554 | The second function, "rouse_wait", waits for the callback to be called |
453 | (by calling "schedule" to go to sleep) and returns the arguments |
555 | (by calling "schedule" to go to sleep) and returns the arguments |
454 | originally passed to the callback. |
556 | originally passed to the callback. |
455 | |
557 | |
… | |
… | |
469 | you can roll your own, using "schedule": |
571 | you can roll your own, using "schedule": |
470 | |
572 | |
471 | sub wait_for_child($) { |
573 | sub wait_for_child($) { |
472 | my ($pid) = @_; |
574 | my ($pid) = @_; |
473 | |
575 | |
474 | # store the current coroutine in $current, |
576 | # store the current coro in $current, |
475 | # and provide result variables for the closure passed to ->child |
577 | # and provide result variables for the closure passed to ->child |
476 | my $current = $Coro::current; |
578 | my $current = $Coro::current; |
477 | my ($done, $rstatus); |
579 | my ($done, $rstatus); |
478 | |
580 | |
479 | # pass a closure to ->child |
581 | # pass a closure to ->child |
… | |
… | |
490 | |
592 | |
491 | BUGS/LIMITATIONS |
593 | BUGS/LIMITATIONS |
492 | fork with pthread backend |
594 | fork with pthread backend |
493 | When Coro is compiled using the pthread backend (which isn't |
595 | When Coro is compiled using the pthread backend (which isn't |
494 | recommended but required on many BSDs as their libcs are completely |
596 | recommended but required on many BSDs as their libcs are completely |
495 | broken), then coroutines will not survive a fork. There is no known |
597 | broken), then coro will not survive a fork. There is no known |
496 | workaround except to fix your libc and use a saner backend. |
598 | workaround except to fix your libc and use a saner backend. |
497 | |
599 | |
498 | perl process emulation ("threads") |
600 | perl process emulation ("threads") |
499 | This module is not perl-pseudo-thread-safe. You should only ever use |
601 | This module is not perl-pseudo-thread-safe. You should only ever use |
500 | this module from the first thread (this requirement might be removed |
602 | this module from the first thread (this requirement might be removed |
501 | in the future to allow per-thread schedulers, but Coro::State does |
603 | in the future to allow per-thread schedulers, but Coro::State does |
502 | not yet allow this). I recommend disabling thread support and using |
604 | not yet allow this). I recommend disabling thread support and using |
503 | processes, as having the windows process emulation enabled under |
605 | processes, as having the windows process emulation enabled under |
504 | unix roughly halves perl performance, even when not used. |
606 | unix roughly halves perl performance, even when not used. |
505 | |
607 | |
506 | coroutine switching not signal safe |
608 | coro switching is not signal safe |
507 | You must not switch to another coroutine from within a signal |
609 | You must not switch to another coro from within a signal handler |
508 | handler (only relevant with %SIG - most event libraries provide safe |
610 | (only relevant with %SIG - most event libraries provide safe |
509 | signals). |
611 | signals). |
510 | |
612 | |
511 | That means you *MUST NOT* call any function that might "block" the |
613 | That means you *MUST NOT* call any function that might "block" the |
512 | current coroutine - "cede", "schedule" "Coro::Semaphore->down" or |
614 | current coro - "cede", "schedule" "Coro::Semaphore->down" or |
513 | anything that calls those. Everything else, including calling |
615 | anything that calls those. Everything else, including calling |
514 | "ready", works. |
616 | "ready", works. |
515 | |
617 | |
516 | SEE ALSO |
618 | SEE ALSO |
517 | Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event. |
619 | Event-Loop integration: Coro::AnyEvent, Coro::EV, Coro::Event. |