1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - coroutine process abstraction |
3 | Coro - the only real threads in perl |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro; |
7 | use Coro; |
8 | |
8 | |
… | |
… | |
11 | print "2\n"; |
11 | print "2\n"; |
12 | cede; # yield back to main |
12 | cede; # yield back to main |
13 | print "4\n"; |
13 | print "4\n"; |
14 | }; |
14 | }; |
15 | print "1\n"; |
15 | print "1\n"; |
16 | cede; # yield to coroutine |
16 | cede; # yield to coro |
17 | print "3\n"; |
17 | print "3\n"; |
18 | cede; # and again |
18 | cede; # and again |
19 | |
19 | |
20 | # use locking |
20 | # use locking |
21 | use Coro::Semaphore; |
21 | use Coro::Semaphore; |
… | |
… | |
26 | $locked = 1; |
26 | $locked = 1; |
27 | $lock->up; |
27 | $lock->up; |
28 | |
28 | |
29 | =head1 DESCRIPTION |
29 | =head1 DESCRIPTION |
30 | |
30 | |
31 | This module collection manages coroutines. Coroutines are similar to |
31 | For a tutorial-style introduction, please read the L<Coro::Intro> |
32 | threads but don't (in general) run in parallel at the same time even |
32 | manpage. This manpage mainly contains reference information. |
33 | on SMP machines. The specific flavor of coroutine used in this module |
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34 | also guarantees you that it will not switch between coroutines unless |
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35 | necessary, at easily-identified points in your program, so locking and |
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36 | parallel access are rarely an issue, making coroutine programming much |
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37 | safer and easier than threads programming. |
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38 | |
33 | |
39 | Unlike a normal perl program, however, coroutines allow you to have |
34 | This module collection manages continuations in general, most often in |
40 | multiple running interpreters that share data, which is especially useful |
35 | the form of cooperative threads (also called coros, or simply "coro" |
41 | to code pseudo-parallel processes and for event-based programming, such as |
36 | in the documentation). They are similar to kernel threads but don't (in |
42 | multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to |
37 | general) run in parallel at the same time even on SMP machines. The |
43 | learn more. |
38 | specific flavor of thread offered by this module also guarantees you that |
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39 | it will not switch between threads unless necessary, at easily-identified |
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40 | points in your program, so locking and parallel access are rarely an |
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41 | issue, making thread programming much safer and easier than using other |
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42 | thread models. |
44 | |
43 | |
45 | Coroutines are also useful because Perl has no support for threads (the so |
44 | Unlike the so-called "Perl threads" (which are not actually real threads |
46 | called "threads" that perl offers are nothing more than the (bad) process |
45 | but only the windows process emulation (see section of same name for more |
47 | emulation coming from the Windows platform: On standard operating systems |
46 | details) ported to unix, and as such act as processes), Coro provides |
48 | they serve no purpose whatsoever, except by making your programs slow and |
47 | a full shared address space, which makes communication between threads |
49 | making them use a lot of memory. Best disable them when building perl, or |
48 | very easy. And Coro's threads are fast, too: disabling the Windows |
50 | aks your software vendor/distributor to do it for you). |
49 | process emulation code in your perl and using Coro can easily result in |
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50 | a two to four times speed increase for your programs. A parallel matrix |
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51 | multiplication benchmark runs over 300 times faster on a single core than |
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52 | perl's pseudo-threads on a quad core using all four cores. |
51 | |
53 | |
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54 | Coro achieves that by supporting multiple running interpreters that share |
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55 | data, which is especially useful to code pseudo-parallel processes and |
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56 | for event-based programming, such as multiple HTTP-GET requests running |
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57 | concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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58 | into an event-based environment. |
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59 | |
52 | In this module, coroutines are defined as "callchain + lexical variables + |
60 | In this module, a thread is defined as "callchain + lexical variables + |
53 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
61 | some package variables + C stack), that is, a thread has its own callchain, |
54 | its own set of lexicals and its own set of perls most important global |
62 | its own set of lexicals and its own set of perls most important global |
55 | variables (see L<Coro::State> for more configuration). |
63 | variables (see L<Coro::State> for more configuration and background info). |
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64 | |
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65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
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66 | module family is quite large. |
56 | |
67 | |
57 | =cut |
68 | =cut |
58 | |
69 | |
59 | package Coro; |
70 | package Coro; |
60 | |
71 | |
61 | use strict qw(vars subs); |
72 | use strict qw(vars subs); |
62 | no warnings "uninitialized"; |
73 | no warnings "uninitialized"; |
63 | |
74 | |
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75 | use Guard (); |
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76 | |
64 | use Coro::State; |
77 | use Coro::State; |
65 | |
78 | |
66 | use base qw(Coro::State Exporter); |
79 | use base qw(Coro::State Exporter); |
67 | |
80 | |
68 | our $idle; # idle handler |
81 | our $idle; # idle handler |
69 | our $main; # main coroutine |
82 | our $main; # main coro |
70 | our $current; # current coroutine |
83 | our $current; # current coro |
71 | |
84 | |
72 | our $VERSION = 4.901; |
85 | our $VERSION = 5.17; |
73 | |
86 | |
74 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
87 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
75 | our %EXPORT_TAGS = ( |
88 | our %EXPORT_TAGS = ( |
76 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
89 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
77 | ); |
90 | ); |
78 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
91 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
79 | |
92 | |
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93 | =head1 GLOBAL VARIABLES |
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94 | |
80 | =over 4 |
95 | =over 4 |
81 | |
96 | |
82 | =item $Coro::main |
97 | =item $Coro::main |
83 | |
98 | |
84 | This variable stores the coroutine object that represents the main |
99 | This variable stores the Coro object that represents the main |
85 | program. While you cna C<ready> it and do most other things you can do to |
100 | program. While you cna C<ready> it and do most other things you can do to |
86 | coroutines, it is mainly useful to compare again C<$Coro::current>, to see |
101 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
87 | whether you are running in the main program or not. |
102 | whether you are running in the main program or not. |
88 | |
103 | |
89 | =cut |
104 | =cut |
90 | |
105 | |
91 | $main = new Coro; |
106 | # $main is now being initialised by Coro::State |
92 | |
107 | |
93 | =item $Coro::current |
108 | =item $Coro::current |
94 | |
109 | |
95 | The coroutine object representing the current coroutine (the last |
110 | The Coro object representing the current coro (the last |
96 | coroutine that the Coro scheduler switched to). The initial value is |
111 | coro that the Coro scheduler switched to). The initial value is |
97 | C<$main> (of course). |
112 | C<$Coro::main> (of course). |
98 | |
113 | |
99 | This variable is B<strictly> I<read-only>. You can take copies of the |
114 | This variable is B<strictly> I<read-only>. You can take copies of the |
100 | value stored in it and use it as any other coroutine object, but you must |
115 | value stored in it and use it as any other Coro object, but you must |
101 | not otherwise modify the variable itself. |
116 | not otherwise modify the variable itself. |
102 | |
117 | |
103 | =cut |
118 | =cut |
104 | |
119 | |
105 | $main->{desc} = "[main::]"; |
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106 | |
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107 | # maybe some other module used Coro::Specific before... |
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108 | $main->{_specific} = $current->{_specific} |
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109 | if $current; |
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110 | |
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111 | _set_current $main; |
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112 | |
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113 | sub current() { $current } # [DEPRECATED] |
120 | sub current() { $current } # [DEPRECATED] |
114 | |
121 | |
115 | =item $Coro::idle |
122 | =item $Coro::idle |
116 | |
123 | |
117 | This variable is mainly useful to integrate Coro into event loops. It is |
124 | This variable is mainly useful to integrate Coro into event loops. It is |
118 | usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is |
125 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
119 | pretty low-level functionality. |
126 | pretty low-level functionality. |
120 | |
127 | |
121 | This variable stores a callback that is called whenever the scheduler |
128 | This variable stores either a Coro object or a callback. |
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129 | |
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130 | If it is a callback, the it is called whenever the scheduler finds no |
122 | finds no ready coroutines to run. The default implementation prints |
131 | ready coros to run. The default implementation prints "FATAL: |
123 | "FATAL: deadlock detected" and exits, because the program has no other way |
132 | deadlock detected" and exits, because the program has no other way to |
124 | to continue. |
133 | continue. |
125 | |
134 | |
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135 | If it is a coro object, then this object will be readied (without |
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136 | invoking any ready hooks, however) when the scheduler finds no other ready |
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137 | coros to run. |
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138 | |
126 | This hook is overwritten by modules such as C<Coro::Timer> and |
139 | This hook is overwritten by modules such as C<Coro::EV> and |
127 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
140 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
128 | coroutine so the scheduler can run it. |
141 | coro so the scheduler can run it. |
129 | |
142 | |
130 | Note that the callback I<must not>, under any circumstances, block |
143 | Note that the callback I<must not>, under any circumstances, block |
131 | the current coroutine. Normally, this is achieved by having an "idle |
144 | the current coro. Normally, this is achieved by having an "idle |
132 | coroutine" that calls the event loop and then blocks again, and then |
145 | coro" that calls the event loop and then blocks again, and then |
133 | readying that coroutine in the idle handler. |
146 | readying that coro in the idle handler, or by simply placing the idle |
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147 | coro in this variable. |
134 | |
148 | |
135 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
149 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
136 | technique. |
150 | technique. |
137 | |
151 | |
138 | Please note that if your callback recursively invokes perl (e.g. for event |
152 | Please note that if your callback recursively invokes perl (e.g. for event |
… | |
… | |
143 | $idle = sub { |
157 | $idle = sub { |
144 | require Carp; |
158 | require Carp; |
145 | Carp::croak ("FATAL: deadlock detected"); |
159 | Carp::croak ("FATAL: deadlock detected"); |
146 | }; |
160 | }; |
147 | |
161 | |
148 | sub _cancel { |
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149 | my ($self) = @_; |
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150 | |
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151 | # free coroutine data and mark as destructed |
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152 | $self->_destroy |
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153 | or return; |
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154 | |
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155 | # call all destruction callbacks |
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156 | $_->(@{$self->{_status}}) |
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157 | for @{ delete $self->{_on_destroy} || [] }; |
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158 | } |
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159 | |
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160 | # this coroutine is necessary because a coroutine |
162 | # this coro is necessary because a coro |
161 | # cannot destroy itself. |
163 | # cannot destroy itself. |
162 | my @destroy; |
164 | our @destroy; |
163 | my $manager; |
165 | our $manager; |
164 | |
166 | |
165 | $manager = new Coro sub { |
167 | $manager = new Coro sub { |
166 | while () { |
168 | while () { |
167 | (shift @destroy)->_cancel |
169 | Coro::State::cancel shift @destroy |
168 | while @destroy; |
170 | while @destroy; |
169 | |
171 | |
170 | &schedule; |
172 | &schedule; |
171 | } |
173 | } |
172 | }; |
174 | }; |
173 | $manager->{desc} = "[coro manager]"; |
175 | $manager->{desc} = "[coro manager]"; |
174 | $manager->prio (PRIO_MAX); |
176 | $manager->prio (PRIO_MAX); |
175 | |
177 | |
176 | =back |
178 | =back |
177 | |
179 | |
178 | =head2 SIMPLE COROUTINE CREATION |
180 | =head1 SIMPLE CORO CREATION |
179 | |
181 | |
180 | =over 4 |
182 | =over 4 |
181 | |
183 | |
182 | =item async { ... } [@args...] |
184 | =item async { ... } [@args...] |
183 | |
185 | |
184 | Create a new coroutine and return it's coroutine object (usually |
186 | Create a new coro and return its Coro object (usually |
185 | unused). The coroutine will be put into the ready queue, so |
187 | unused). The coro will be put into the ready queue, so |
186 | it will start running automatically on the next scheduler run. |
188 | it will start running automatically on the next scheduler run. |
187 | |
189 | |
188 | The first argument is a codeblock/closure that should be executed in the |
190 | The first argument is a codeblock/closure that should be executed in the |
189 | coroutine. When it returns argument returns the coroutine is automatically |
191 | coro. When it returns argument returns the coro is automatically |
190 | terminated. |
192 | terminated. |
191 | |
193 | |
192 | The remaining arguments are passed as arguments to the closure. |
194 | The remaining arguments are passed as arguments to the closure. |
193 | |
195 | |
194 | See the C<Coro::State::new> constructor for info about the coroutine |
196 | See the C<Coro::State::new> constructor for info about the coro |
195 | environment in which coroutines are executed. |
197 | environment in which coro are executed. |
196 | |
198 | |
197 | Calling C<exit> in a coroutine will do the same as calling exit outside |
199 | Calling C<exit> in a coro will do the same as calling exit outside |
198 | the coroutine. Likewise, when the coroutine dies, the program will exit, |
200 | the coro. Likewise, when the coro dies, the program will exit, |
199 | just as it would in the main program. |
201 | just as it would in the main program. |
200 | |
202 | |
201 | If you do not want that, you can provide a default C<die> handler, or |
203 | If you do not want that, you can provide a default C<die> handler, or |
202 | simply avoid dieing (by use of C<eval>). |
204 | simply avoid dieing (by use of C<eval>). |
203 | |
205 | |
204 | Example: Create a new coroutine that just prints its arguments. |
206 | Example: Create a new coro that just prints its arguments. |
205 | |
207 | |
206 | async { |
208 | async { |
207 | print "@_\n"; |
209 | print "@_\n"; |
208 | } 1,2,3,4; |
210 | } 1,2,3,4; |
209 | |
211 | |
210 | =cut |
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211 | |
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212 | sub async(&@) { |
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213 | my $coro = new Coro @_; |
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214 | $coro->ready; |
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215 | $coro |
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216 | } |
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217 | |
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218 | =item async_pool { ... } [@args...] |
212 | =item async_pool { ... } [@args...] |
219 | |
213 | |
220 | Similar to C<async>, but uses a coroutine pool, so you should not call |
214 | Similar to C<async>, but uses a coro pool, so you should not call |
221 | terminate or join on it (although you are allowed to), and you get a |
215 | terminate or join on it (although you are allowed to), and you get a |
222 | coroutine that might have executed other code already (which can be good |
216 | coro that might have executed other code already (which can be good |
223 | or bad :). |
217 | or bad :). |
224 | |
218 | |
225 | On the plus side, this function is faster than creating (and destroying) |
219 | On the plus side, this function is about twice as fast as creating (and |
226 | a completly new coroutine, so if you need a lot of generic coroutines in |
220 | destroying) a completely new coro, so if you need a lot of generic |
227 | quick successsion, use C<async_pool>, not C<async>. |
221 | coros in quick successsion, use C<async_pool>, not C<async>. |
228 | |
222 | |
229 | The code block is executed in an C<eval> context and a warning will be |
223 | The code block is executed in an C<eval> context and a warning will be |
230 | issued in case of an exception instead of terminating the program, as |
224 | issued in case of an exception instead of terminating the program, as |
231 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
225 | C<async> does. As the coro is being reused, stuff like C<on_destroy> |
232 | will not work in the expected way, unless you call terminate or cancel, |
226 | will not work in the expected way, unless you call terminate or cancel, |
233 | which somehow defeats the purpose of pooling (but is fine in the |
227 | which somehow defeats the purpose of pooling (but is fine in the |
234 | exceptional case). |
228 | exceptional case). |
235 | |
229 | |
236 | The priority will be reset to C<0> after each run, tracing will be |
230 | The priority will be reset to C<0> after each run, tracing will be |
237 | disabled, the description will be reset and the default output filehandle |
231 | disabled, the description will be reset and the default output filehandle |
238 | gets restored, so you can change all these. Otherwise the coroutine will |
232 | gets restored, so you can change all these. Otherwise the coro will |
239 | be re-used "as-is": most notably if you change other per-coroutine global |
233 | be re-used "as-is": most notably if you change other per-coro global |
240 | stuff such as C<$/> you I<must needs> revert that change, which is most |
234 | stuff such as C<$/> you I<must needs> revert that change, which is most |
241 | simply done by using local as in: C<< local $/ >>. |
235 | simply done by using local as in: C<< local $/ >>. |
242 | |
236 | |
243 | The idle pool size is limited to C<8> idle coroutines (this can be |
237 | The idle pool size is limited to C<8> idle coros (this can be |
244 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
238 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
245 | coros as required. |
239 | coros as required. |
246 | |
240 | |
247 | If you are concerned about pooled coroutines growing a lot because a |
241 | If you are concerned about pooled coros growing a lot because a |
248 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
242 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
249 | { terminate }> once per second or so to slowly replenish the pool. In |
243 | { terminate }> once per second or so to slowly replenish the pool. In |
250 | addition to that, when the stacks used by a handler grows larger than 16kb |
244 | addition to that, when the stacks used by a handler grows larger than 32kb |
251 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
245 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
252 | |
246 | |
253 | =cut |
247 | =cut |
254 | |
248 | |
255 | our $POOL_SIZE = 8; |
249 | our $POOL_SIZE = 8; |
256 | our $POOL_RSS = 16 * 1024; |
250 | our $POOL_RSS = 32 * 1024; |
257 | our @async_pool; |
251 | our @async_pool; |
258 | |
252 | |
259 | sub pool_handler { |
253 | sub pool_handler { |
260 | my $cb; |
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261 | |
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262 | while () { |
254 | while () { |
263 | eval { |
255 | eval { |
264 | while () { |
256 | &{&_pool_handler} while 1; |
265 | _pool_1 $cb; |
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266 | &$cb; |
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267 | _pool_2 $cb; |
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268 | &schedule; |
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269 | } |
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270 | }; |
257 | }; |
271 | |
258 | |
272 | if ($@) { |
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273 | last if $@ eq "\3async_pool terminate\2\n"; |
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274 | warn $@; |
259 | warn $@ if $@; |
275 | } |
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276 | } |
260 | } |
277 | } |
261 | } |
278 | |
262 | |
279 | sub async_pool(&@) { |
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280 | # this is also inlined into the unlock_scheduler |
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281 | my $coro = (pop @async_pool) || new Coro \&pool_handler; |
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282 | |
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283 | $coro->{_invoke} = [@_]; |
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284 | $coro->ready; |
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285 | |
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286 | $coro |
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287 | } |
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288 | |
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289 | =back |
263 | =back |
290 | |
264 | |
291 | =head2 STATIC METHODS |
265 | =head1 STATIC METHODS |
292 | |
266 | |
293 | Static methods are actually functions that operate on the current coroutine. |
267 | Static methods are actually functions that implicitly operate on the |
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268 | current coro. |
294 | |
269 | |
295 | =over 4 |
270 | =over 4 |
296 | |
271 | |
297 | =item schedule |
272 | =item schedule |
298 | |
273 | |
299 | Calls the scheduler. The scheduler will find the next coroutine that is |
274 | Calls the scheduler. The scheduler will find the next coro that is |
300 | to be run from the ready queue and switches to it. The next coroutine |
275 | to be run from the ready queue and switches to it. The next coro |
301 | to be run is simply the one with the highest priority that is longest |
276 | to be run is simply the one with the highest priority that is longest |
302 | in its ready queue. If there is no coroutine ready, it will clal the |
277 | in its ready queue. If there is no coro ready, it will clal the |
303 | C<$Coro::idle> hook. |
278 | C<$Coro::idle> hook. |
304 | |
279 | |
305 | Please note that the current coroutine will I<not> be put into the ready |
280 | Please note that the current coro will I<not> be put into the ready |
306 | queue, so calling this function usually means you will never be called |
281 | queue, so calling this function usually means you will never be called |
307 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
282 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
308 | thus waking you up. |
283 | thus waking you up. |
309 | |
284 | |
310 | This makes C<schedule> I<the> generic method to use to block the current |
285 | This makes C<schedule> I<the> generic method to use to block the current |
311 | coroutine and wait for events: first you remember the current coroutine in |
286 | coro and wait for events: first you remember the current coro in |
312 | a variable, then arrange for some callback of yours to call C<< ->ready |
287 | a variable, then arrange for some callback of yours to call C<< ->ready |
313 | >> on that once some event happens, and last you call C<schedule> to put |
288 | >> on that once some event happens, and last you call C<schedule> to put |
314 | yourself to sleep. Note that a lot of things can wake your coroutine up, |
289 | yourself to sleep. Note that a lot of things can wake your coro up, |
315 | so you need to check whether the event indeed happened, e.g. by storing the |
290 | so you need to check whether the event indeed happened, e.g. by storing the |
316 | status in a variable. |
291 | status in a variable. |
317 | |
292 | |
318 | The canonical way to wait on external events is this: |
293 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
319 | |
294 | |
320 | { |
295 | =item cede |
321 | # remember current coroutine |
|
|
322 | my $current = $Coro::current; |
|
|
323 | |
296 | |
324 | # register a hypothetical event handler |
297 | "Cede" to other coros. This function puts the current coro into |
325 | on_event_invoke sub { |
298 | the ready queue and calls C<schedule>, which has the effect of giving |
326 | # wake up sleeping coroutine |
299 | up the current "timeslice" to other coros of the same or higher |
327 | $current->ready; |
300 | priority. Once your coro gets its turn again it will automatically be |
328 | undef $current; |
301 | resumed. |
|
|
302 | |
|
|
303 | This function is often called C<yield> in other languages. |
|
|
304 | |
|
|
305 | =item Coro::cede_notself |
|
|
306 | |
|
|
307 | Works like cede, but is not exported by default and will cede to I<any> |
|
|
308 | coro, regardless of priority. This is useful sometimes to ensure |
|
|
309 | progress is made. |
|
|
310 | |
|
|
311 | =item terminate [arg...] |
|
|
312 | |
|
|
313 | Terminates the current coro with the given status values (see L<cancel>). |
|
|
314 | |
|
|
315 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
|
|
316 | |
|
|
317 | These function install enter and leave winders in the current scope. The |
|
|
318 | enter block will be executed when on_enter is called and whenever the |
|
|
319 | current coro is re-entered by the scheduler, while the leave block is |
|
|
320 | executed whenever the current coro is blocked by the scheduler, and |
|
|
321 | also when the containing scope is exited (by whatever means, be it exit, |
|
|
322 | die, last etc.). |
|
|
323 | |
|
|
324 | I<Neither invoking the scheduler, nor exceptions, are allowed within those |
|
|
325 | BLOCKs>. That means: do not even think about calling C<die> without an |
|
|
326 | eval, and do not even think of entering the scheduler in any way. |
|
|
327 | |
|
|
328 | Since both BLOCKs are tied to the current scope, they will automatically |
|
|
329 | be removed when the current scope exits. |
|
|
330 | |
|
|
331 | These functions implement the same concept as C<dynamic-wind> in scheme |
|
|
332 | does, and are useful when you want to localise some resource to a specific |
|
|
333 | coro. |
|
|
334 | |
|
|
335 | They slow down thread switching considerably for coros that use them |
|
|
336 | (about 40% for a BLOCK with a single assignment, so thread switching is |
|
|
337 | still reasonably fast if the handlers are fast). |
|
|
338 | |
|
|
339 | These functions are best understood by an example: The following function |
|
|
340 | will change the current timezone to "Antarctica/South_Pole", which |
|
|
341 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
|
|
342 | which remember/change the current timezone and restore the previous |
|
|
343 | value, respectively, the timezone is only changed for the coro that |
|
|
344 | installed those handlers. |
|
|
345 | |
|
|
346 | use POSIX qw(tzset); |
|
|
347 | |
|
|
348 | async { |
|
|
349 | my $old_tz; # store outside TZ value here |
|
|
350 | |
|
|
351 | Coro::on_enter { |
|
|
352 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
353 | |
|
|
354 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
|
355 | tzset; # enable new value |
329 | }; |
356 | }; |
330 | |
357 | |
331 | # call schedule until event occurred. |
358 | Coro::on_leave { |
332 | # in case we are woken up for other reasons |
359 | $ENV{TZ} = $old_tz; |
333 | # (current still defined), loop. |
360 | tzset; # restore old value |
334 | Coro::schedule while $current; |
361 | }; |
|
|
362 | |
|
|
363 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
364 | # without disturbing the TZ of any other coro. |
335 | } |
365 | }; |
336 | |
366 | |
337 | =item cede |
367 | This can be used to localise about any resource (locale, uid, current |
|
|
368 | working directory etc.) to a block, despite the existance of other |
|
|
369 | coros. |
338 | |
370 | |
339 | "Cede" to other coroutines. This function puts the current coroutine into |
371 | Another interesting example implements time-sliced multitasking using |
340 | the ready queue and calls C<schedule>, which has the effect of giving |
372 | interval timers (this could obviously be optimised, but does the job): |
341 | up the current "timeslice" to other coroutines of the same or higher |
|
|
342 | priority. Once your coroutine gets its turn again it will automatically be |
|
|
343 | resumed. |
|
|
344 | |
373 | |
345 | This function is often called C<yield> in other languages. |
374 | # "timeslice" the given block |
|
|
375 | sub timeslice(&) { |
|
|
376 | use Time::HiRes (); |
346 | |
377 | |
347 | =item Coro::cede_notself |
378 | Coro::on_enter { |
|
|
379 | # on entering the thread, we set an VTALRM handler to cede |
|
|
380 | $SIG{VTALRM} = sub { cede }; |
|
|
381 | # and then start the interval timer |
|
|
382 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
383 | }; |
|
|
384 | Coro::on_leave { |
|
|
385 | # on leaving the thread, we stop the interval timer again |
|
|
386 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
387 | }; |
348 | |
388 | |
349 | Works like cede, but is not exported by default and will cede to I<any> |
389 | &{+shift}; |
350 | coroutine, regardless of priority. This is useful sometimes to ensure |
390 | } |
351 | progress is made. |
|
|
352 | |
391 | |
353 | =item terminate [arg...] |
392 | # use like this: |
|
|
393 | timeslice { |
|
|
394 | # The following is an endless loop that would normally |
|
|
395 | # monopolise the process. Since it runs in a timesliced |
|
|
396 | # environment, it will regularly cede to other threads. |
|
|
397 | while () { } |
|
|
398 | }; |
354 | |
399 | |
355 | Terminates the current coroutine with the given status values (see L<cancel>). |
|
|
356 | |
400 | |
357 | =item killall |
401 | =item killall |
358 | |
402 | |
359 | Kills/terminates/cancels all coroutines except the currently running |
403 | Kills/terminates/cancels all coros except the currently running one. |
360 | one. This is useful after a fork, either in the child or the parent, as |
|
|
361 | usually only one of them should inherit the running coroutines. |
|
|
362 | |
404 | |
363 | Note that while this will try to free some of the main programs resources, |
405 | Note that while this will try to free some of the main interpreter |
|
|
406 | resources if the calling coro isn't the main coro, but one |
364 | you cannot free all of them, so if a coroutine that is not the main |
407 | cannot free all of them, so if a coro that is not the main coro |
365 | program calls this function, there will be some one-time resource leak. |
408 | calls this function, there will be some one-time resource leak. |
366 | |
409 | |
367 | =cut |
410 | =cut |
368 | |
|
|
369 | sub terminate { |
|
|
370 | $current->cancel (@_); |
|
|
371 | } |
|
|
372 | |
411 | |
373 | sub killall { |
412 | sub killall { |
374 | for (Coro::State::list) { |
413 | for (Coro::State::list) { |
375 | $_->cancel |
414 | $_->cancel |
376 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
415 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
377 | } |
416 | } |
378 | } |
417 | } |
379 | |
418 | |
380 | =back |
419 | =back |
381 | |
420 | |
382 | =head2 COROUTINE METHODS |
421 | =head1 CORO OBJECT METHODS |
383 | |
422 | |
384 | These are the methods you can call on coroutine objects (or to create |
423 | These are the methods you can call on coro objects (or to create |
385 | them). |
424 | them). |
386 | |
425 | |
387 | =over 4 |
426 | =over 4 |
388 | |
427 | |
389 | =item new Coro \&sub [, @args...] |
428 | =item new Coro \&sub [, @args...] |
390 | |
429 | |
391 | Create a new coroutine and return it. When the sub returns, the coroutine |
430 | Create a new coro and return it. When the sub returns, the coro |
392 | automatically terminates as if C<terminate> with the returned values were |
431 | automatically terminates as if C<terminate> with the returned values were |
393 | called. To make the coroutine run you must first put it into the ready |
432 | called. To make the coro run you must first put it into the ready |
394 | queue by calling the ready method. |
433 | queue by calling the ready method. |
395 | |
434 | |
396 | See C<async> and C<Coro::State::new> for additional info about the |
435 | See C<async> and C<Coro::State::new> for additional info about the |
397 | coroutine environment. |
436 | coro environment. |
398 | |
437 | |
399 | =cut |
438 | =cut |
400 | |
439 | |
401 | sub _run_coro { |
440 | sub _coro_run { |
402 | terminate &{+shift}; |
441 | terminate &{+shift}; |
403 | } |
442 | } |
404 | |
443 | |
405 | sub new { |
|
|
406 | my $class = shift; |
|
|
407 | |
|
|
408 | $class->SUPER::new (\&_run_coro, @_) |
|
|
409 | } |
|
|
410 | |
|
|
411 | =item $success = $coroutine->ready |
444 | =item $success = $coro->ready |
412 | |
445 | |
413 | Put the given coroutine into the end of its ready queue (there is one |
446 | Put the given coro into the end of its ready queue (there is one |
414 | queue for each priority) and return true. If the coroutine is already in |
447 | queue for each priority) and return true. If the coro is already in |
415 | the ready queue, do nothing and return false. |
448 | the ready queue, do nothing and return false. |
416 | |
449 | |
417 | This ensures that the scheduler will resume this coroutine automatically |
450 | This ensures that the scheduler will resume this coro automatically |
418 | once all the coroutines of higher priority and all coroutines of the same |
451 | once all the coro of higher priority and all coro of the same |
419 | priority that were put into the ready queue earlier have been resumed. |
452 | priority that were put into the ready queue earlier have been resumed. |
420 | |
453 | |
|
|
454 | =item $coro->suspend |
|
|
455 | |
|
|
456 | Suspends the specified coro. A suspended coro works just like any other |
|
|
457 | coro, except that the scheduler will not select a suspended coro for |
|
|
458 | execution. |
|
|
459 | |
|
|
460 | Suspending a coro can be useful when you want to keep the coro from |
|
|
461 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
462 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
463 | |
|
|
464 | A scenario for the former would be to suspend all (other) coros after a |
|
|
465 | fork and keep them alive, so their destructors aren't called, but new |
|
|
466 | coros can be created. |
|
|
467 | |
|
|
468 | =item $coro->resume |
|
|
469 | |
|
|
470 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
471 | the coro was in the ready queue when it was suspended, it might have been |
|
|
472 | unreadied by the scheduler, so an activation might have been lost. |
|
|
473 | |
|
|
474 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
475 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
476 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
477 | that. |
|
|
478 | |
421 | =item $is_ready = $coroutine->is_ready |
479 | =item $is_ready = $coro->is_ready |
422 | |
480 | |
423 | Return whether the coroutine is currently the ready queue or not, |
481 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
|
|
482 | object gets destroyed, it will eventually be scheduled by the scheduler. |
424 | |
483 | |
|
|
484 | =item $is_running = $coro->is_running |
|
|
485 | |
|
|
486 | Returns true iff the Coro object is currently running. Only one Coro object |
|
|
487 | can ever be in the running state (but it currently is possible to have |
|
|
488 | multiple running Coro::States). |
|
|
489 | |
|
|
490 | =item $is_suspended = $coro->is_suspended |
|
|
491 | |
|
|
492 | Returns true iff this Coro object has been suspended. Suspended Coros will |
|
|
493 | not ever be scheduled. |
|
|
494 | |
425 | =item $coroutine->cancel (arg...) |
495 | =item $coro->cancel (arg...) |
426 | |
496 | |
427 | Terminates the given coroutine and makes it return the given arguments as |
497 | Terminates the given Coro and makes it return the given arguments as |
428 | status (default: the empty list). Never returns if the coroutine is the |
498 | status (default: the empty list). Never returns if the Coro is the |
429 | current coroutine. |
499 | current Coro. |
430 | |
500 | |
431 | =cut |
501 | =cut |
432 | |
502 | |
433 | sub cancel { |
503 | sub cancel { |
434 | my $self = shift; |
504 | my $self = shift; |
435 | $self->{_status} = [@_]; |
|
|
436 | |
505 | |
437 | if ($current == $self) { |
506 | if ($current == $self) { |
438 | push @destroy, $self; |
507 | terminate @_; |
439 | $manager->ready; |
|
|
440 | &schedule while 1; |
|
|
441 | } else { |
508 | } else { |
442 | $self->_cancel; |
509 | $self->{_status} = [@_]; |
|
|
510 | Coro::State::cancel $self; |
443 | } |
511 | } |
444 | } |
512 | } |
445 | |
513 | |
|
|
514 | =item $coro->schedule_to |
|
|
515 | |
|
|
516 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
|
|
517 | of continuing with the next coro from the ready queue, always switch to |
|
|
518 | the given coro object (regardless of priority etc.). The readyness |
|
|
519 | state of that coro isn't changed. |
|
|
520 | |
|
|
521 | This is an advanced method for special cases - I'd love to hear about any |
|
|
522 | uses for this one. |
|
|
523 | |
|
|
524 | =item $coro->cede_to |
|
|
525 | |
|
|
526 | Like C<schedule_to>, but puts the current coro into the ready |
|
|
527 | queue. This has the effect of temporarily switching to the given |
|
|
528 | coro, and continuing some time later. |
|
|
529 | |
|
|
530 | This is an advanced method for special cases - I'd love to hear about any |
|
|
531 | uses for this one. |
|
|
532 | |
446 | =item $coroutine->throw ([$scalar]) |
533 | =item $coro->throw ([$scalar]) |
447 | |
534 | |
448 | If C<$throw> is specified and defined, it will be thrown as an exception |
535 | If C<$throw> is specified and defined, it will be thrown as an exception |
449 | inside the coroutine at the next convenient point in time (usually after |
536 | inside the coro at the next convenient point in time. Otherwise |
450 | it gains control at the next schedule/transfer/cede). Otherwise clears the |
|
|
451 | exception object. |
537 | clears the exception object. |
|
|
538 | |
|
|
539 | Coro will check for the exception each time a schedule-like-function |
|
|
540 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
|
|
541 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
|
|
542 | detect this case and return early in case an exception is pending. |
452 | |
543 | |
453 | The exception object will be thrown "as is" with the specified scalar in |
544 | The exception object will be thrown "as is" with the specified scalar in |
454 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
545 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
455 | (unlike with C<die>). |
546 | (unlike with C<die>). |
456 | |
547 | |
457 | This can be used as a softer means than C<cancel> to ask a coroutine to |
548 | This can be used as a softer means than C<cancel> to ask a coro to |
458 | end itself, although there is no guarantee that the exception will lead to |
549 | end itself, although there is no guarantee that the exception will lead to |
459 | termination, and if the exception isn't caught it might well end the whole |
550 | termination, and if the exception isn't caught it might well end the whole |
460 | program. |
551 | program. |
461 | |
552 | |
462 | You might also think of C<throw> as being the moral equivalent of |
553 | You might also think of C<throw> as being the moral equivalent of |
463 | C<kill>ing a coroutine with a signal (in this case, a scalar). |
554 | C<kill>ing a coro with a signal (in this case, a scalar). |
464 | |
555 | |
465 | =item $coroutine->join |
556 | =item $coro->join |
466 | |
557 | |
467 | Wait until the coroutine terminates and return any values given to the |
558 | Wait until the coro terminates and return any values given to the |
468 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
559 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
469 | from multiple coroutines, and all will be resumed and given the status |
560 | from multiple coro, and all will be resumed and given the status |
470 | return once the C<$coroutine> terminates. |
561 | return once the C<$coro> terminates. |
471 | |
562 | |
472 | =cut |
563 | =cut |
473 | |
564 | |
474 | sub join { |
565 | sub join { |
475 | my $self = shift; |
566 | my $self = shift; |
… | |
… | |
486 | } |
577 | } |
487 | |
578 | |
488 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
579 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
489 | } |
580 | } |
490 | |
581 | |
491 | =item $coroutine->on_destroy (\&cb) |
582 | =item $coro->on_destroy (\&cb) |
492 | |
583 | |
493 | Registers a callback that is called when this coroutine gets destroyed, |
584 | Registers a callback that is called when this coro gets destroyed, |
494 | but before it is joined. The callback gets passed the terminate arguments, |
585 | but before it is joined. The callback gets passed the terminate arguments, |
495 | if any, and I<must not> die, under any circumstances. |
586 | if any, and I<must not> die, under any circumstances. |
496 | |
587 | |
497 | =cut |
588 | =cut |
498 | |
589 | |
… | |
… | |
500 | my ($self, $cb) = @_; |
591 | my ($self, $cb) = @_; |
501 | |
592 | |
502 | push @{ $self->{_on_destroy} }, $cb; |
593 | push @{ $self->{_on_destroy} }, $cb; |
503 | } |
594 | } |
504 | |
595 | |
505 | =item $oldprio = $coroutine->prio ($newprio) |
596 | =item $oldprio = $coro->prio ($newprio) |
506 | |
597 | |
507 | Sets (or gets, if the argument is missing) the priority of the |
598 | Sets (or gets, if the argument is missing) the priority of the |
508 | coroutine. Higher priority coroutines get run before lower priority |
599 | coro. Higher priority coro get run before lower priority |
509 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
600 | coro. Priorities are small signed integers (currently -4 .. +3), |
510 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
601 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
511 | to get then): |
602 | to get then): |
512 | |
603 | |
513 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
604 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
514 | 3 > 1 > 0 > -1 > -3 > -4 |
605 | 3 > 1 > 0 > -1 > -3 > -4 |
515 | |
606 | |
516 | # set priority to HIGH |
607 | # set priority to HIGH |
517 | current->prio(PRIO_HIGH); |
608 | current->prio (PRIO_HIGH); |
518 | |
609 | |
519 | The idle coroutine ($Coro::idle) always has a lower priority than any |
610 | The idle coro ($Coro::idle) always has a lower priority than any |
520 | existing coroutine. |
611 | existing coro. |
521 | |
612 | |
522 | Changing the priority of the current coroutine will take effect immediately, |
613 | Changing the priority of the current coro will take effect immediately, |
523 | but changing the priority of coroutines in the ready queue (but not |
614 | but changing the priority of coro in the ready queue (but not |
524 | running) will only take effect after the next schedule (of that |
615 | running) will only take effect after the next schedule (of that |
525 | coroutine). This is a bug that will be fixed in some future version. |
616 | coro). This is a bug that will be fixed in some future version. |
526 | |
617 | |
527 | =item $newprio = $coroutine->nice ($change) |
618 | =item $newprio = $coro->nice ($change) |
528 | |
619 | |
529 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
620 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
530 | higher values mean lower priority, just as in unix). |
621 | higher values mean lower priority, just as in unix). |
531 | |
622 | |
532 | =item $olddesc = $coroutine->desc ($newdesc) |
623 | =item $olddesc = $coro->desc ($newdesc) |
533 | |
624 | |
534 | Sets (or gets in case the argument is missing) the description for this |
625 | Sets (or gets in case the argument is missing) the description for this |
535 | coroutine. This is just a free-form string you can associate with a |
626 | coro. This is just a free-form string you can associate with a |
536 | coroutine. |
627 | coro. |
537 | |
628 | |
538 | This method simply sets the C<< $coroutine->{desc} >> member to the given |
629 | This method simply sets the C<< $coro->{desc} >> member to the given |
539 | string. You can modify this member directly if you wish. |
630 | string. You can modify this member directly if you wish. |
540 | |
631 | |
541 | =cut |
632 | =cut |
542 | |
633 | |
543 | sub desc { |
634 | sub desc { |
544 | my $old = $_[0]{desc}; |
635 | my $old = $_[0]{desc}; |
545 | $_[0]{desc} = $_[1] if @_ > 1; |
636 | $_[0]{desc} = $_[1] if @_ > 1; |
546 | $old; |
637 | $old; |
547 | } |
638 | } |
548 | |
639 | |
|
|
640 | sub transfer { |
|
|
641 | require Carp; |
|
|
642 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
643 | } |
|
|
644 | |
549 | =back |
645 | =back |
550 | |
646 | |
551 | =head2 GLOBAL FUNCTIONS |
647 | =head1 GLOBAL FUNCTIONS |
552 | |
648 | |
553 | =over 4 |
649 | =over 4 |
554 | |
650 | |
555 | =item Coro::nready |
651 | =item Coro::nready |
556 | |
652 | |
557 | Returns the number of coroutines that are currently in the ready state, |
653 | Returns the number of coro that are currently in the ready state, |
558 | i.e. that can be switched to by calling C<schedule> directory or |
654 | i.e. that can be switched to by calling C<schedule> directory or |
559 | indirectly. The value C<0> means that the only runnable coroutine is the |
655 | indirectly. The value C<0> means that the only runnable coro is the |
560 | currently running one, so C<cede> would have no effect, and C<schedule> |
656 | currently running one, so C<cede> would have no effect, and C<schedule> |
561 | would cause a deadlock unless there is an idle handler that wakes up some |
657 | would cause a deadlock unless there is an idle handler that wakes up some |
562 | coroutines. |
658 | coro. |
563 | |
659 | |
564 | =item my $guard = Coro::guard { ... } |
660 | =item my $guard = Coro::guard { ... } |
565 | |
661 | |
566 | This creates and returns a guard object. Nothing happens until the object |
662 | This function still exists, but is deprecated. Please use the |
567 | gets destroyed, in which case the codeblock given as argument will be |
663 | C<Guard::guard> function instead. |
568 | executed. This is useful to free locks or other resources in case of a |
|
|
569 | runtime error or when the coroutine gets canceled, as in both cases the |
|
|
570 | guard block will be executed. The guard object supports only one method, |
|
|
571 | C<< ->cancel >>, which will keep the codeblock from being executed. |
|
|
572 | |
664 | |
573 | Example: set some flag and clear it again when the coroutine gets canceled |
|
|
574 | or the function returns: |
|
|
575 | |
|
|
576 | sub do_something { |
|
|
577 | my $guard = Coro::guard { $busy = 0 }; |
|
|
578 | $busy = 1; |
|
|
579 | |
|
|
580 | # do something that requires $busy to be true |
|
|
581 | } |
|
|
582 | |
|
|
583 | =cut |
665 | =cut |
584 | |
666 | |
585 | sub guard(&) { |
667 | BEGIN { *guard = \&Guard::guard } |
586 | bless \(my $cb = $_[0]), "Coro::guard" |
|
|
587 | } |
|
|
588 | |
|
|
589 | sub Coro::guard::cancel { |
|
|
590 | ${$_[0]} = sub { }; |
|
|
591 | } |
|
|
592 | |
|
|
593 | sub Coro::guard::DESTROY { |
|
|
594 | ${$_[0]}->(); |
|
|
595 | } |
|
|
596 | |
|
|
597 | |
668 | |
598 | =item unblock_sub { ... } |
669 | =item unblock_sub { ... } |
599 | |
670 | |
600 | This utility function takes a BLOCK or code reference and "unblocks" it, |
671 | This utility function takes a BLOCK or code reference and "unblocks" it, |
601 | returning a new coderef. Unblocking means that calling the new coderef |
672 | returning a new coderef. Unblocking means that calling the new coderef |
602 | will return immediately without blocking, returning nothing, while the |
673 | will return immediately without blocking, returning nothing, while the |
603 | original code ref will be called (with parameters) from within another |
674 | original code ref will be called (with parameters) from within another |
604 | coroutine. |
675 | coro. |
605 | |
676 | |
606 | The reason this function exists is that many event libraries (such as the |
677 | The reason this function exists is that many event libraries (such as the |
607 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
678 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
608 | of thread-safety). This means you must not block within event callbacks, |
679 | of reentrancy). This means you must not block within event callbacks, |
609 | otherwise you might suffer from crashes or worse. The only event library |
680 | otherwise you might suffer from crashes or worse. The only event library |
610 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
681 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
611 | |
682 | |
612 | This function allows your callbacks to block by executing them in another |
683 | This function allows your callbacks to block by executing them in another |
613 | coroutine where it is safe to block. One example where blocking is handy |
684 | coro where it is safe to block. One example where blocking is handy |
614 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
685 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
615 | disk, for example. |
686 | disk, for example. |
616 | |
687 | |
617 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
688 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
618 | creating event callbacks that want to block. |
689 | creating event callbacks that want to block. |
619 | |
690 | |
620 | If your handler does not plan to block (e.g. simply sends a message to |
691 | If your handler does not plan to block (e.g. simply sends a message to |
621 | another coroutine, or puts some other coroutine into the ready queue), |
692 | another coro, or puts some other coro into the ready queue), there is |
622 | there is no reason to use C<unblock_sub>. |
693 | no reason to use C<unblock_sub>. |
623 | |
694 | |
624 | Note that you also need to use C<unblock_sub> for any other callbacks that |
695 | Note that you also need to use C<unblock_sub> for any other callbacks that |
625 | are indirectly executed by any C-based event loop. For example, when you |
696 | are indirectly executed by any C-based event loop. For example, when you |
626 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
697 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
627 | provides callbacks that are the result of some event callback, then you |
698 | provides callbacks that are the result of some event callback, then you |
… | |
… | |
636 | # return immediately and can be reused) and because we cannot cede |
707 | # return immediately and can be reused) and because we cannot cede |
637 | # inside an event callback. |
708 | # inside an event callback. |
638 | our $unblock_scheduler = new Coro sub { |
709 | our $unblock_scheduler = new Coro sub { |
639 | while () { |
710 | while () { |
640 | while (my $cb = pop @unblock_queue) { |
711 | while (my $cb = pop @unblock_queue) { |
641 | # this is an inlined copy of async_pool |
712 | &async_pool (@$cb); |
642 | my $coro = (pop @async_pool) || new Coro \&pool_handler; |
|
|
643 | |
713 | |
644 | $coro->{_invoke} = $cb; |
|
|
645 | $coro->ready; |
|
|
646 | cede; # for short-lived callbacks, this reduces pressure on the coro pool |
714 | # for short-lived callbacks, this reduces pressure on the coro pool |
|
|
715 | # as the chance is very high that the async_poll coro will be back |
|
|
716 | # in the idle state when cede returns |
|
|
717 | cede; |
647 | } |
718 | } |
648 | schedule; # sleep well |
719 | schedule; # sleep well |
649 | } |
720 | } |
650 | }; |
721 | }; |
651 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
722 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
… | |
… | |
657 | unshift @unblock_queue, [$cb, @_]; |
728 | unshift @unblock_queue, [$cb, @_]; |
658 | $unblock_scheduler->ready; |
729 | $unblock_scheduler->ready; |
659 | } |
730 | } |
660 | } |
731 | } |
661 | |
732 | |
|
|
733 | =item $cb = Coro::rouse_cb |
|
|
734 | |
|
|
735 | Create and return a "rouse callback". That's a code reference that, |
|
|
736 | when called, will remember a copy of its arguments and notify the owner |
|
|
737 | coro of the callback. |
|
|
738 | |
|
|
739 | See the next function. |
|
|
740 | |
|
|
741 | =item @args = Coro::rouse_wait [$cb] |
|
|
742 | |
|
|
743 | Wait for the specified rouse callback (or the last one that was created in |
|
|
744 | this coro). |
|
|
745 | |
|
|
746 | As soon as the callback is invoked (or when the callback was invoked |
|
|
747 | before C<rouse_wait>), it will return the arguments originally passed to |
|
|
748 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
749 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
750 | statement at the end. |
|
|
751 | |
|
|
752 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
|
|
753 | |
662 | =back |
754 | =back |
663 | |
755 | |
664 | =cut |
756 | =cut |
665 | |
757 | |
666 | 1; |
758 | 1; |
667 | |
759 | |
|
|
760 | =head1 HOW TO WAIT FOR A CALLBACK |
|
|
761 | |
|
|
762 | It is very common for a coro to wait for some callback to be |
|
|
763 | called. This occurs naturally when you use coro in an otherwise |
|
|
764 | event-based program, or when you use event-based libraries. |
|
|
765 | |
|
|
766 | These typically register a callback for some event, and call that callback |
|
|
767 | when the event occured. In a coro, however, you typically want to |
|
|
768 | just wait for the event, simplyifying things. |
|
|
769 | |
|
|
770 | For example C<< AnyEvent->child >> registers a callback to be called when |
|
|
771 | a specific child has exited: |
|
|
772 | |
|
|
773 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
774 | |
|
|
775 | But from within a coro, you often just want to write this: |
|
|
776 | |
|
|
777 | my $status = wait_for_child $pid; |
|
|
778 | |
|
|
779 | Coro offers two functions specifically designed to make this easy, |
|
|
780 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
|
|
781 | |
|
|
782 | The first function, C<rouse_cb>, generates and returns a callback that, |
|
|
783 | when invoked, will save its arguments and notify the coro that |
|
|
784 | created the callback. |
|
|
785 | |
|
|
786 | The second function, C<rouse_wait>, waits for the callback to be called |
|
|
787 | (by calling C<schedule> to go to sleep) and returns the arguments |
|
|
788 | originally passed to the callback. |
|
|
789 | |
|
|
790 | Using these functions, it becomes easy to write the C<wait_for_child> |
|
|
791 | function mentioned above: |
|
|
792 | |
|
|
793 | sub wait_for_child($) { |
|
|
794 | my ($pid) = @_; |
|
|
795 | |
|
|
796 | my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
|
|
797 | |
|
|
798 | my ($rpid, $rstatus) = Coro::rouse_wait; |
|
|
799 | $rstatus |
|
|
800 | } |
|
|
801 | |
|
|
802 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
|
|
803 | you can roll your own, using C<schedule>: |
|
|
804 | |
|
|
805 | sub wait_for_child($) { |
|
|
806 | my ($pid) = @_; |
|
|
807 | |
|
|
808 | # store the current coro in $current, |
|
|
809 | # and provide result variables for the closure passed to ->child |
|
|
810 | my $current = $Coro::current; |
|
|
811 | my ($done, $rstatus); |
|
|
812 | |
|
|
813 | # pass a closure to ->child |
|
|
814 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
815 | $rstatus = $_[1]; # remember rstatus |
|
|
816 | $done = 1; # mark $rstatus as valud |
|
|
817 | }); |
|
|
818 | |
|
|
819 | # wait until the closure has been called |
|
|
820 | schedule while !$done; |
|
|
821 | |
|
|
822 | $rstatus |
|
|
823 | } |
|
|
824 | |
|
|
825 | |
668 | =head1 BUGS/LIMITATIONS |
826 | =head1 BUGS/LIMITATIONS |
669 | |
827 | |
|
|
828 | =over 4 |
|
|
829 | |
|
|
830 | =item fork with pthread backend |
|
|
831 | |
|
|
832 | When Coro is compiled using the pthread backend (which isn't recommended |
|
|
833 | but required on many BSDs as their libcs are completely broken), then |
|
|
834 | coro will not survive a fork. There is no known workaround except to |
|
|
835 | fix your libc and use a saner backend. |
|
|
836 | |
|
|
837 | =item perl process emulation ("threads") |
|
|
838 | |
670 | This module is not perl-pseudo-thread-safe. You should only ever use this |
839 | This module is not perl-pseudo-thread-safe. You should only ever use this |
671 | module from the same thread (this requirement might be removed in the |
840 | module from the first thread (this requirement might be removed in the |
672 | future to allow per-thread schedulers, but Coro::State does not yet allow |
841 | future to allow per-thread schedulers, but Coro::State does not yet allow |
673 | this). I recommend disabling thread support and using processes, as this |
842 | this). I recommend disabling thread support and using processes, as having |
674 | is much faster and uses less memory. |
843 | the windows process emulation enabled under unix roughly halves perl |
|
|
844 | performance, even when not used. |
|
|
845 | |
|
|
846 | =item coro switching is not signal safe |
|
|
847 | |
|
|
848 | You must not switch to another coro from within a signal handler |
|
|
849 | (only relevant with %SIG - most event libraries provide safe signals). |
|
|
850 | |
|
|
851 | That means you I<MUST NOT> call any function that might "block" the |
|
|
852 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
|
|
853 | anything that calls those. Everything else, including calling C<ready>, |
|
|
854 | works. |
|
|
855 | |
|
|
856 | =back |
|
|
857 | |
|
|
858 | |
|
|
859 | =head1 WINDOWS PROCESS EMULATION |
|
|
860 | |
|
|
861 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
862 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
863 | while in the same mail making rather confused statements about perl |
|
|
864 | ithreads (for example, that memory or files would be shared), showing his |
|
|
865 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
866 | it is probably not obvious to everybody). |
|
|
867 | |
|
|
868 | What follows is an ultra-condensed version of my talk about threads in |
|
|
869 | scripting languages given onthe perl workshop 2009: |
|
|
870 | |
|
|
871 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
872 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
873 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
874 | |
|
|
875 | It does that by using threads instead of OS processes. The difference |
|
|
876 | between processes and threads is that threads share memory (and other |
|
|
877 | state, such as files) between threads within a single process, while |
|
|
878 | processes do not share anything (at least not semantically). That |
|
|
879 | means that modifications done by one thread are seen by others, while |
|
|
880 | modifications by one process are not seen by other processes. |
|
|
881 | |
|
|
882 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
883 | process, all state is copied (memory is copied physically, files and code |
|
|
884 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
885 | the same behaviour can be achieved by using operating system processes, |
|
|
886 | except that UNIX typically uses hardware built into the system to do this |
|
|
887 | efficiently, while the windows process emulation emulates this hardware in |
|
|
888 | software (rather efficiently, but of course it is still much slower than |
|
|
889 | dedicated hardware). |
|
|
890 | |
|
|
891 | As mentioned before, loading code, modifying code, modifying data |
|
|
892 | structures and so on is only visible in the ithreads process doing the |
|
|
893 | modification, not in other ithread processes within the same OS process. |
|
|
894 | |
|
|
895 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
896 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
897 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
898 | by the forks module, which gives you the (i-) threads API, just much |
|
|
899 | faster). |
|
|
900 | |
|
|
901 | Sharing data is in the i-threads model is done by transfering data |
|
|
902 | structures between threads using copying semantics, which is very slow - |
|
|
903 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
904 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
905 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
906 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
907 | real threads, refer to my talk for details). |
|
|
908 | |
|
|
909 | As summary, i-threads *use* threads to implement processes, while |
|
|
910 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
911 | processes. I-threads slow down every perl program when enabled, and |
|
|
912 | outside of windows, serve no (or little) practical purpose, but |
|
|
913 | disadvantages every single-threaded Perl program. |
|
|
914 | |
|
|
915 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
916 | misleading as it implies that it implements some kind of thread model for |
|
|
917 | perl, and prefer the name "windows process emulation", which describes the |
|
|
918 | actual use and behaviour of it much better. |
675 | |
919 | |
676 | =head1 SEE ALSO |
920 | =head1 SEE ALSO |
677 | |
921 | |
678 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
922 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
679 | |
923 | |
680 | Debugging: L<Coro::Debug>. |
924 | Debugging: L<Coro::Debug>. |
681 | |
925 | |
682 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
926 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
683 | |
927 | |
684 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
928 | Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
929 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
685 | |
930 | |
686 | IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
931 | I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
687 | |
932 | |
688 | Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. |
933 | Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
934 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
935 | L<Coro::Select>. |
689 | |
936 | |
690 | XS API: L<Coro::MakeMaker>. |
937 | XS API: L<Coro::MakeMaker>. |
691 | |
938 | |
692 | Low level Configuration, Coroutine Environment: L<Coro::State>. |
939 | Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
693 | |
940 | |
694 | =head1 AUTHOR |
941 | =head1 AUTHOR |
695 | |
942 | |
696 | Marc Lehmann <schmorp@schmorp.de> |
943 | Marc Lehmann <schmorp@schmorp.de> |
697 | http://home.schmorp.de/ |
944 | http://home.schmorp.de/ |