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4SYNOPSIS 4SYNOPSIS
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";
10 cede; # yield back to main
11 print "4\n";
9 }; 12 };
13 print "1\n";
14 cede; # yield to coroutine
15 print "3\n";
16 cede; # and again
10 17
11 # alternatively create an async coroutine like this: 18 # use locking
19 my $lock = new Coro::Semaphore;
20 my $locked;
12 21
13 sub some_func : Coro { 22 $lock->down;
14 # some more async code 23 $locked = 1;
15 } 24 $lock->up;
16
17 cede;
18 25
19DESCRIPTION 26DESCRIPTION
20 This module collection manages coroutines. Coroutines are similar to 27 This module collection manages coroutines. Coroutines are similar to
21 threads but don't run in parallel. 28 threads but don't run in parallel at the same time even on SMP machines.
29 The specific flavor of coroutine used in this module also guarantees you
30 that it will not switch between coroutines unless necessary, at
31 easily-identified points in your program, so locking and parallel access
32 are rarely an issue, making coroutine programming much safer than
33 threads programming.
34
35 (Perl, however, does not natively support real threads but instead does
36 a very slow and memory-intensive emulation of processes using threads.
37 This is a performance win on Windows machines, and a loss everywhere
38 else).
22 39
23 In this module, coroutines are defined as "callchain + lexical variables 40 In this module, coroutines are defined as "callchain + lexical variables
24 + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 41 + @_ + $_ + $@ + $/ + 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 42 callchain, its own set of lexicals and its own set of perls most
26 important global variables. 43 important global variables (see Coro::State for more configuration).
27 44
28 $main 45 $main
29 This coroutine represents the main program. 46 This coroutine represents the main program.
30 47
31 $current (or as function: current) 48 $current (or as function: current)
32 The current coroutine (the last coroutine switched to). The initial 49 The current coroutine (the last coroutine switched to). The initial
33 value is $main (of course). 50 value is $main (of course).
34 51
35 This variable is strictly *read-only*. It is provided for 52 This variable is strictly *read-only*. It is provided for
36 performance reasons. If performance is not essentiel you are 53 performance reasons. If performance is not essential you are
37 encouraged to use the "Coro::current" function instead. 54 encouraged to use the "Coro::current" function instead.
38 55
39 $idle 56 $idle
40 A callback that is called whenever the scheduler finds no ready 57 A callback that is called whenever the scheduler finds no ready
41 coroutines to run. The default implementation prints "FATAL: 58 coroutines to run. The default implementation prints "FATAL:
… …
45 This hook is overwritten by modules such as "Coro::Timer" and 62 This hook is overwritten by modules such as "Coro::Timer" and
46 "Coro::Event" to wait on an external event that hopefully wake up a 63 "Coro::Event" to wait on an external event that hopefully wake up a
47 coroutine so the scheduler can run it. 64 coroutine so the scheduler can run it.
48 65
49 Please note that if your callback recursively invokes perl (e.g. for 66 Please note that if your callback recursively invokes perl (e.g. for
50 event handlers), then it must be prepared to be called recursively. 67 event handlers), then it must be prepared to be called recursively
68 itself.
51 69
52 STATIC METHODS 70 STATIC METHODS
53 Static methods are actually functions that operate on the current 71 Static methods are actually functions that operate on the current
54 coroutine only. 72 coroutine only.
55 73
56 async { ... } [@args...] 74 async { ... } [@args...]
57 Create a new asynchronous coroutine and return it's coroutine object 75 Create a new asynchronous coroutine and return it's coroutine object
58 (usually unused). When the sub returns the new coroutine is 76 (usually unused). When the sub returns the new coroutine is
59 automatically terminated. 77 automatically terminated.
60 78
61 Calling "exit" in a coroutine will not work correctly, so do not do 79 See the "Coro::State::new" constructor for info about the coroutine
62 that. 80 environment in which coroutines run.
63 81
64 When the coroutine dies, the program will exit, just as in the main 82 Calling "exit" in a coroutine will do the same as calling exit
65 program. 83 outside the coroutine. Likewise, when the coroutine dies, the
84 program will exit, just as it would in the main program.
66 85
67 # create a new coroutine that just prints its arguments 86 # create a new coroutine that just prints its arguments
68 async { 87 async {
69 print "@_\n"; 88 print "@_\n";
70 } 1,2,3,4; 89 } 1,2,3,4;
90
91 async_pool { ... } [@args...]
92 Similar to "async", but uses a coroutine pool, so you should not
93 call terminate or join (although you are allowed to), and you get a
94 coroutine that might have executed other code already (which can be
95 good or bad :).
96
97 Also, the block is executed in an "eval" context and a warning will
98 be issued in case of an exception instead of terminating the
99 program, as "async" does. As the coroutine is being reused, stuff
100 like "on_destroy" will not work in the expected way, unless you call
101 terminate or cancel, which somehow defeats the purpose of pooling.
102
103 The priority will be reset to 0 after each job, tracing will be
104 disabled, the description will be reset and the default output
105 filehandle gets restored, so you can change alkl these. Otherwise
106 the coroutine will be re-used "as-is": most notably if you change
107 other per-coroutine global stuff such as $/ you need to revert that
108 change, which is most simply done by using local as in " local $/ ".
109
110 The pool size is limited to 8 idle coroutines (this can be adjusted
111 by changing $Coro::POOL_SIZE), and there can be as many non-idle
112 coros as required.
113
114 If you are concerned about pooled coroutines growing a lot because a
115 single "async_pool" used a lot of stackspace you can e.g.
116 "async_pool { terminate }" once per second or so to slowly replenish
117 the pool. In addition to that, when the stacks used by a handler
118 grows larger than 16kb (adjustable with $Coro::POOL_RSS) it will
119 also exit.
71 120
72 schedule 121 schedule
73 Calls the scheduler. Please note that the current coroutine will not 122 Calls the scheduler. Please note that the current coroutine will not
74 be put into the ready queue, so calling this function usually means 123 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 124 you will never be called again unless something else (e.g. an event
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86 # wake up sleeping coroutine 135 # wake up sleeping coroutine
87 $current->ready; 136 $current->ready;
88 undef $current; 137 undef $current;
89 }; 138 };
90 139
91 # call schedule until event occured. 140 # call schedule until event occurred.
92 # in case we are woken up for other reasons 141 # in case we are woken up for other reasons
93 # (current still defined), loop. 142 # (current still defined), loop.
94 Coro::schedule while $current; 143 Coro::schedule while $current;
95 } 144 }
96 145
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98 "Cede" to other coroutines. This function puts the current coroutine 147 "Cede" to other coroutines. This function puts the current coroutine
99 into the ready queue and calls "schedule", which has the effect of 148 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 149 giving up the current "timeslice" to other coroutines of the same or
101 higher priority. 150 higher priority.
102 151
152 Coro::cede_notself
153 Works like cede, but is not exported by default and will cede to any
154 coroutine, regardless of priority, once.
155
103 terminate [arg...] 156 terminate [arg...]
104 Terminates the current coroutine with the given status values (see 157 Terminates the current coroutine with the given status values (see
105 cancel). 158 cancel).
159
160 killall
161 Kills/terminates/cancels all coroutines except the currently running
162 one. This is useful after a fork, either in the child or the parent,
163 as usually only one of them should inherit the running coroutines.
106 164
107 # dynamic methods 165 # dynamic methods
108 166
109 COROUTINE METHODS 167 COROUTINE METHODS
110 These are the methods you can call on coroutine objects. 168 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 171 Create a new coroutine and return it. When the sub returns the
114 coroutine automatically terminates as if "terminate" with the 172 coroutine automatically terminates as if "terminate" with the
115 returned values were called. To make the coroutine run you must 173 returned values were called. To make the coroutine run you must
116 first put it into the ready queue by calling the ready method. 174 first put it into the ready queue by calling the ready method.
117 175
118 Calling "exit" in a coroutine will not work correctly, so do not do 176 See "async" and "Coro::State::new" for additional info about the
119 that. 177 coroutine environment.
120 178
121 $success = $coroutine->ready 179 $success = $coroutine->ready
122 Put the given coroutine into the ready queue (according to it's 180 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 181 priority) and return true. If the coroutine is already in the ready
124 queue, do nothing and return false. 182 queue, do nothing and return false.
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126 $is_ready = $coroutine->is_ready 184 $is_ready = $coroutine->is_ready
127 Return wether the coroutine is currently the ready queue or not, 185 Return wether the coroutine is currently the ready queue or not,
128 186
129 $coroutine->cancel (arg...) 187 $coroutine->cancel (arg...)
130 Terminates the given coroutine and makes it return the given 188 Terminates the given coroutine and makes it return the given
131 arguments as status (default: the empty list). 189 arguments as status (default: the empty list). Never returns if the
190 coroutine is the current coroutine.
132 191
133 $coroutine->join 192 $coroutine->join
134 Wait until the coroutine terminates and return any values given to 193 Wait until the coroutine terminates and return any values given to
135 the "terminate" or "cancel" functions. "join" can be called multiple 194 the "terminate" or "cancel" functions. "join" can be called
136 times from multiple coroutine. 195 concurrently from multiple coroutines.
196
197 $coroutine->on_destroy (\&cb)
198 Registers a callback that is called when this coroutine gets
199 destroyed, but before it is joined. The callback gets passed the
200 terminate arguments, if any.
137 201
138 $oldprio = $coroutine->prio ($newprio) 202 $oldprio = $coroutine->prio ($newprio)
139 Sets (or gets, if the argument is missing) the priority of the 203 Sets (or gets, if the argument is missing) the priority of the
140 coroutine. Higher priority coroutines get run before lower priority 204 coroutine. Higher priority coroutines get run before lower priority
141 coroutines. Priorities are small signed integers (currently -4 .. 205 coroutines. Priorities are small signed integers (currently -4 ..
… …
164 $olddesc = $coroutine->desc ($newdesc) 228 $olddesc = $coroutine->desc ($newdesc)
165 Sets (or gets in case the argument is missing) the description for 229 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 230 this coroutine. This is just a free-form string you can associate
167 with a coroutine. 231 with a coroutine.
168 232
169 UTILITY FUNCTIONS 233 This method simply sets the "$coroutine->{desc}" member to the given
234 string. You can modify this member directly if you wish.
235
236 $coroutine->throw ([$scalar])
237 If $throw is specified and defined, it will be thrown as an
238 exception inside the coroutine at the next convinient point in time
239 (usually after it gains control at the next schedule/transfer/cede).
240 Otherwise clears the exception object.
241
242 The exception object will be thrown "as is" with the specified
243 scalar in $@, i.e. if it is a string, no line number or newline will
244 be appended (unlike with "die").
245
246 This can be used as a softer means than "cancel" to ask a coroutine
247 to end itself, although there is no guarentee that the exception
248 will lead to termination, and if the exception isn't caught it might
249 well end the whole program.
250
251 GLOBAL FUNCTIONS
252 Coro::nready
253 Returns the number of coroutines that are currently in the ready
254 state, i.e. that can be switched to. The value 0 means that the only
255 runnable coroutine is the currently running one, so "cede" would
256 have no effect, and "schedule" would cause a deadlock unless there
257 is an idle handler that wakes up some coroutines.
258
259 my $guard = Coro::guard { ... }
260 This creates and returns a guard object. Nothing happens until the
261 object gets destroyed, in which case the codeblock given as argument
262 will be executed. This is useful to free locks or other resources in
263 case of a runtime error or when the coroutine gets canceled, as in
264 both cases the guard block will be executed. The guard object
265 supports only one method, "->cancel", which will keep the codeblock
266 from being executed.
267
268 Example: set some flag and clear it again when the coroutine gets
269 canceled or the function returns:
270
271 sub do_something {
272 my $guard = Coro::guard { $busy = 0 };
273 $busy = 1;
274
275 # do something that requires $busy to be true
276 }
277
170 unblock_sub { ... } 278 unblock_sub { ... }
171 This utility function takes a BLOCK or code reference and "unblocks" 279 This utility function takes a BLOCK or code reference and "unblocks"
172 it, returning the new coderef. This means that the new coderef will 280 it, returning the new coderef. This means that the new coderef will
173 return immediately without blocking, returning nothing, while the 281 return immediately without blocking, returning nothing, while the
174 original code ref will be called (with parameters) from within its 282 original code ref will be called (with parameters) from within its
175 own coroutine. 283 own coroutine.
176 284
177 The reason this fucntion exists is that many event libraries (such 285 The reason this function exists is that many event libraries (such
178 as the venerable Event module) are not coroutine-safe (a weaker form 286 as the venerable Event module) are not coroutine-safe (a weaker form
179 of thread-safety). This means you must not block within event 287 of thread-safety). This means you must not block within event
180 callbacks, otherwise you might suffer from crashes or worse. 288 callbacks, otherwise you might suffer from crashes or worse.
181 289
182 This function allows your callbacks to block by executing them in 290 This function allows your callbacks to block by executing them in
… …
190BUGS/LIMITATIONS 298BUGS/LIMITATIONS
191 - you must make very sure that no coro is still active on global 299 - you must make very sure that no coro is still active on global
192 destruction. very bad things might happen otherwise (usually segfaults). 300 destruction. very bad things might happen otherwise (usually segfaults).
193 301
194 - this module is not thread-safe. You should only ever use this module 302 - 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 303 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 304 to allow per-thread schedulers, but Coro::State does not yet allow
197 this). 305 this).
198 306
199SEE ALSO 307SEE ALSO
308 Lower level Configuration, Coroutine Environment: Coro::State.
309
310 Debugging: Coro::Debug.
311
200 Support/Utility: Coro::Cont, Coro::Specific, Coro::State, Coro::Util. 312 Support/Utility: Coro::Specific, Coro::Util.
201 313
202 Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore, 314 Locking/IPC: Coro::Signal, Coro::Channel, Coro::Semaphore,
203 Coro::SemaphoreSet, Coro::RWLock. 315 Coro::SemaphoreSet, Coro::RWLock.
204 316
205 Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket, 317 Event/IO: Coro::Timer, Coro::Event, Coro::Handle, Coro::Socket.
206 Coro::Select.
207 318
319 Compatibility: Coro::LWP, Coro::Storable, Coro::Select.
320
208 Embedding: <Coro:MakeMaker> 321 Embedding: <Coro:MakeMaker>.
209 322
210AUTHOR 323AUTHOR
211 Marc Lehmann <schmorp@schmorp.de> 324 Marc Lehmann <schmorp@schmorp.de>
212 http://home.schmorp.de/ 325 http://home.schmorp.de/
213 326

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