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16 | |
16 | |
17 | cede; |
17 | cede; |
18 | |
18 | |
19 | DESCRIPTION |
19 | DESCRIPTION |
20 | This module collection manages coroutines. Coroutines are similar to |
20 | This module collection manages coroutines. Coroutines are similar to |
21 | threads but don't run in parallel. |
21 | threads but don't run in parallel at the same time even on SMP machines. |
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22 | The specific flavor of coroutine used in this module also guarantees you |
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23 | that it will not switch between coroutines unless necessary, at |
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24 | easily-identified points in your program, so locking and parallel access |
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25 | are rarely an issue, making coroutine programming much safer than |
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26 | threads programming. |
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27 | |
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28 | (Perl, however, does not natively support real threads but instead does |
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29 | a very slow and memory-intensive emulation of processes using threads. |
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30 | This is a performance win on Windows machines, and a loss everywhere |
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31 | else). |
22 | |
32 | |
23 | In this module, coroutines are defined as "callchain + lexical variables |
33 | In this module, coroutines are defined as "callchain + lexical variables |
24 | + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own |
34 | + @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own |
25 | callchain, it's own set of lexicals and it's own set of perl's most |
35 | callchain, its own set of lexicals and its own set of perls most |
26 | important global variables. |
36 | important global variables. |
27 | |
37 | |
28 | $main |
38 | $main |
29 | This coroutine represents the main program. |
39 | This coroutine represents the main program. |
30 | |
40 | |
31 | $current (or as function: current) |
41 | $current (or as function: current) |
32 | The current coroutine (the last coroutine switched to). The initial |
42 | The current coroutine (the last coroutine switched to). The initial |
33 | value is $main (of course). |
43 | value is $main (of course). |
34 | |
44 | |
35 | This variable is strictly *read-only*. It is provided for |
45 | This variable is strictly *read-only*. It is provided for |
36 | performance reasons. If performance is not essentiel you are |
46 | performance reasons. If performance is not essential you are |
37 | encouraged to use the "Coro::current" function instead. |
47 | encouraged to use the "Coro::current" function instead. |
38 | |
48 | |
39 | $idle |
49 | $idle |
40 | A callback that is called whenever the scheduler finds no ready |
50 | A callback that is called whenever the scheduler finds no ready |
41 | coroutines to run. The default implementation prints "FATAL: |
51 | coroutines to run. The default implementation prints "FATAL: |
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56 | async { ... } [@args...] |
66 | async { ... } [@args...] |
57 | Create a new asynchronous coroutine and return it's coroutine object |
67 | Create a new asynchronous coroutine and return it's coroutine object |
58 | (usually unused). When the sub returns the new coroutine is |
68 | (usually unused). When the sub returns the new coroutine is |
59 | automatically terminated. |
69 | automatically terminated. |
60 | |
70 | |
61 | Calling "exit" in a coroutine will not work correctly, so do not do |
71 | See the "Coro::State::new" constructor for info about the coroutine |
62 | that. |
72 | environment. |
63 | |
73 | |
64 | When the coroutine dies, the program will exit, just as in the main |
74 | Calling "exit" in a coroutine will do the same as calling exit |
65 | program. |
75 | outside the coroutine. Likewise, when the coroutine dies, the |
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76 | program will exit, just as it would in the main program. |
66 | |
77 | |
67 | # create a new coroutine that just prints its arguments |
78 | # create a new coroutine that just prints its arguments |
68 | async { |
79 | async { |
69 | print "@_\n"; |
80 | print "@_\n"; |
70 | } 1,2,3,4; |
81 | } 1,2,3,4; |
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82 | |
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83 | async_pool { ... } [@args...] |
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84 | Similar to "async", but uses a coroutine pool, so you should not |
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85 | call terminate or join (although you are allowed to), and you get a |
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86 | coroutine that might have executed other code already (which can be |
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87 | good or bad :). |
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88 | |
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89 | Also, the block is executed in an "eval" context and a warning will |
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90 | be issued in case of an exception instead of terminating the |
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91 | program, as "async" does. As the coroutine is being reused, stuff |
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92 | like "on_destroy" will not work in the expected way, unless you call |
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93 | terminate or cancel, which somehow defeats the purpose of pooling. |
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94 | |
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95 | The priority will be reset to 0 after each job, tracing will be |
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96 | disabled, the description will be reset and the default output |
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97 | filehandle gets restored, so you can change alkl these. Otherwise |
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98 | the coroutine will be re-used "as-is": most notably if you change |
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99 | other per-coroutine global stuff such as $/ you need to revert that |
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100 | change, which is most simply done by using local as in " local $/ ". |
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101 | |
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102 | The pool size is limited to 8 idle coroutines (this can be adjusted |
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103 | by changing $Coro::POOL_SIZE), and there can be as many non-idle |
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104 | coros as required. |
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105 | |
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106 | If you are concerned about pooled coroutines growing a lot because a |
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107 | single "async_pool" used a lot of stackspace you can e.g. |
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108 | "async_pool { terminate }" once per second or so to slowly replenish |
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109 | the pool. In addition to that, when the stacks used by a handler |
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110 | grows larger than 16kb (adjustable with $Coro::POOL_RSS) it will |
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111 | also exit. |
71 | |
112 | |
72 | schedule |
113 | schedule |
73 | Calls the scheduler. Please note that the current coroutine will not |
114 | Calls the scheduler. Please note that the current coroutine will not |
74 | be put into the ready queue, so calling this function usually means |
115 | be put into the ready queue, so calling this function usually means |
75 | you will never be called again unless something else (e.g. an event |
116 | you will never be called again unless something else (e.g. an event |
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86 | # wake up sleeping coroutine |
127 | # wake up sleeping coroutine |
87 | $current->ready; |
128 | $current->ready; |
88 | undef $current; |
129 | undef $current; |
89 | }; |
130 | }; |
90 | |
131 | |
91 | # call schedule until event occured. |
132 | # call schedule until event occurred. |
92 | # in case we are woken up for other reasons |
133 | # in case we are woken up for other reasons |
93 | # (current still defined), loop. |
134 | # (current still defined), loop. |
94 | Coro::schedule while $current; |
135 | Coro::schedule while $current; |
95 | } |
136 | } |
96 | |
137 | |
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98 | "Cede" to other coroutines. This function puts the current coroutine |
139 | "Cede" to other coroutines. This function puts the current coroutine |
99 | into the ready queue and calls "schedule", which has the effect of |
140 | into the ready queue and calls "schedule", which has the effect of |
100 | giving up the current "timeslice" to other coroutines of the same or |
141 | giving up the current "timeslice" to other coroutines of the same or |
101 | higher priority. |
142 | higher priority. |
102 | |
143 | |
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144 | Returns true if at least one coroutine switch has happened. |
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145 | |
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146 | Coro::cede_notself |
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147 | Works like cede, but is not exported by default and will cede to any |
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148 | coroutine, regardless of priority, once. |
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149 | |
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150 | Returns true if at least one coroutine switch has happened. |
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151 | |
103 | terminate [arg...] |
152 | terminate [arg...] |
104 | Terminates the current coroutine with the given status values (see |
153 | Terminates the current coroutine with the given status values (see |
105 | cancel). |
154 | cancel). |
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155 | |
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156 | killall |
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157 | Kills/terminates/cancels all coroutines except the currently running |
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158 | one. This is useful after a fork, either in the child or the parent, |
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159 | as usually only one of them should inherit the running coroutines. |
106 | |
160 | |
107 | # dynamic methods |
161 | # dynamic methods |
108 | |
162 | |
109 | COROUTINE METHODS |
163 | COROUTINE METHODS |
110 | These are the methods you can call on coroutine objects. |
164 | These are the methods you can call on coroutine objects. |
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113 | Create a new coroutine and return it. When the sub returns the |
167 | Create a new coroutine and return it. When the sub returns the |
114 | coroutine automatically terminates as if "terminate" with the |
168 | coroutine automatically terminates as if "terminate" with the |
115 | returned values were called. To make the coroutine run you must |
169 | returned values were called. To make the coroutine run you must |
116 | first put it into the ready queue by calling the ready method. |
170 | first put it into the ready queue by calling the ready method. |
117 | |
171 | |
118 | Calling "exit" in a coroutine will not work correctly, so do not do |
172 | See "async" and "Coro::State::new" for additional info about the |
119 | that. |
173 | coroutine environment. |
120 | |
174 | |
121 | $success = $coroutine->ready |
175 | $success = $coroutine->ready |
122 | Put the given coroutine into the ready queue (according to it's |
176 | Put the given coroutine into the ready queue (according to it's |
123 | priority) and return true. If the coroutine is already in the ready |
177 | priority) and return true. If the coroutine is already in the ready |
124 | queue, do nothing and return false. |
178 | queue, do nothing and return false. |
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126 | $is_ready = $coroutine->is_ready |
180 | $is_ready = $coroutine->is_ready |
127 | Return wether the coroutine is currently the ready queue or not, |
181 | Return wether the coroutine is currently the ready queue or not, |
128 | |
182 | |
129 | $coroutine->cancel (arg...) |
183 | $coroutine->cancel (arg...) |
130 | Terminates the given coroutine and makes it return the given |
184 | Terminates the given coroutine and makes it return the given |
131 | arguments as status (default: the empty list). |
185 | arguments as status (default: the empty list). Never returns if the |
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186 | coroutine is the current coroutine. |
132 | |
187 | |
133 | $coroutine->join |
188 | $coroutine->join |
134 | Wait until the coroutine terminates and return any values given to |
189 | Wait until the coroutine terminates and return any values given to |
135 | the "terminate" or "cancel" functions. "join" can be called multiple |
190 | the "terminate" or "cancel" functions. "join" can be called |
136 | times from multiple coroutine. |
191 | concurrently from multiple coroutines. |
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192 | |
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193 | $coroutine->on_destroy (\&cb) |
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194 | Registers a callback that is called when this coroutine gets |
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195 | destroyed, but before it is joined. The callback gets passed the |
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196 | terminate arguments, if any. |
137 | |
197 | |
138 | $oldprio = $coroutine->prio ($newprio) |
198 | $oldprio = $coroutine->prio ($newprio) |
139 | Sets (or gets, if the argument is missing) the priority of the |
199 | Sets (or gets, if the argument is missing) the priority of the |
140 | coroutine. Higher priority coroutines get run before lower priority |
200 | coroutine. Higher priority coroutines get run before lower priority |
141 | coroutines. Priorities are small signed integers (currently -4 .. |
201 | coroutines. Priorities are small signed integers (currently -4 .. |
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164 | $olddesc = $coroutine->desc ($newdesc) |
224 | $olddesc = $coroutine->desc ($newdesc) |
165 | Sets (or gets in case the argument is missing) the description for |
225 | Sets (or gets in case the argument is missing) the description for |
166 | this coroutine. This is just a free-form string you can associate |
226 | this coroutine. This is just a free-form string you can associate |
167 | with a coroutine. |
227 | with a coroutine. |
168 | |
228 | |
169 | UTILITY FUNCTIONS |
229 | This method simply sets the "$coroutine->{desc}" member to the given |
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230 | string. You can modify this member directly if you wish. |
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231 | |
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232 | GLOBAL FUNCTIONS |
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233 | Coro::nready |
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234 | Returns the number of coroutines that are currently in the ready |
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235 | state, i.e. that can be switched to. The value 0 means that the only |
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236 | runnable coroutine is the currently running one, so "cede" would |
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237 | have no effect, and "schedule" would cause a deadlock unless there |
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238 | is an idle handler that wakes up some coroutines. |
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239 | |
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240 | my $guard = Coro::guard { ... } |
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241 | This creates and returns a guard object. Nothing happens until the |
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242 | object gets destroyed, in which case the codeblock given as argument |
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243 | will be executed. This is useful to free locks or other resources in |
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244 | case of a runtime error or when the coroutine gets canceled, as in |
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245 | both cases the guard block will be executed. The guard object |
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246 | supports only one method, "->cancel", which will keep the codeblock |
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247 | from being executed. |
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248 | |
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249 | Example: set some flag and clear it again when the coroutine gets |
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250 | canceled or the function returns: |
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251 | |
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252 | sub do_something { |
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253 | my $guard = Coro::guard { $busy = 0 }; |
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254 | $busy = 1; |
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255 | |
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256 | # do something that requires $busy to be true |
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257 | } |
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258 | |
170 | unblock_sub { ... } |
259 | unblock_sub { ... } |
171 | This utility function takes a BLOCK or code reference and "unblocks" |
260 | This utility function takes a BLOCK or code reference and "unblocks" |
172 | it, returning the new coderef. This means that the new coderef will |
261 | it, returning the new coderef. This means that the new coderef will |
173 | return immediately without blocking, returning nothing, while the |
262 | return immediately without blocking, returning nothing, while the |
174 | original code ref will be called (with parameters) from within its |
263 | original code ref will be called (with parameters) from within its |
175 | own coroutine. |
264 | own coroutine. |
176 | |
265 | |
177 | The reason this fucntion exists is that many event libraries (such |
266 | The reason this function exists is that many event libraries (such |
178 | as the venerable Event module) are not coroutine-safe (a weaker form |
267 | as the venerable Event module) are not coroutine-safe (a weaker form |
179 | of thread-safety). This means you must not block within event |
268 | of thread-safety). This means you must not block within event |
180 | callbacks, otherwise you might suffer from crashes or worse. |
269 | callbacks, otherwise you might suffer from crashes or worse. |
181 | |
270 | |
182 | This function allows your callbacks to block by executing them in |
271 | This function allows your callbacks to block by executing them in |
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190 | BUGS/LIMITATIONS |
279 | BUGS/LIMITATIONS |
191 | - you must make very sure that no coro is still active on global |
280 | - you must make very sure that no coro is still active on global |
192 | destruction. very bad things might happen otherwise (usually segfaults). |
281 | destruction. very bad things might happen otherwise (usually segfaults). |
193 | |
282 | |
194 | - this module is not thread-safe. You should only ever use this module |
283 | - this module is not thread-safe. You should only ever use this module |
195 | from the same thread (this requirement might be losened in the future |
284 | from the same thread (this requirement might be loosened in the future |
196 | to allow per-thread schedulers, but Coro::State does not yet allow |
285 | to allow per-thread schedulers, but Coro::State does not yet allow |
197 | this). |
286 | this). |
198 | |
287 | |
199 | SEE ALSO |
288 | SEE ALSO |
200 | Support/Utility: Coro::Cont, Coro::Specific, Coro::State, Coro::Util. |
289 | Support/Utility: Coro::Specific, Coro::State, Coro::Util. |
201 | |
290 | |
202 | Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
291 | Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, |
203 | Coro::SemaphoreSet, Coro::RWLock. |
292 | Coro::SemaphoreSet, Coro::RWLock. |
204 | |
293 | |
205 | Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket, |
294 | Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket, |