1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - create and manage coroutines |
3 | Coro - real threads in perl |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro; |
7 | use Coro; |
8 | |
8 | |
9 | $new = new Coro sub { |
9 | async { |
10 | print "in coroutine, switching back\n"; |
10 | # some asynchronous thread of execution |
11 | $Coro::main->resume; |
11 | print "2\n"; |
12 | print "in coroutine again, switching back\n"; |
12 | cede; # yield back to main |
13 | $Coro::main->resume; |
13 | print "4\n"; |
14 | }; |
14 | }; |
15 | |
15 | print "1\n"; |
16 | print "in main, switching to coroutine\n"; |
16 | cede; # yield to coroutine |
17 | $new->resume; |
17 | print "3\n"; |
18 | print "back in main, switch to coroutine again\n"; |
18 | cede; # and again |
19 | $new->resume; |
19 | |
20 | print "back in main\n"; |
20 | # use locking |
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21 | use Coro::Semaphore; |
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22 | my $lock = new Coro::Semaphore; |
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23 | my $locked; |
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24 | |
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25 | $lock->down; |
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26 | $locked = 1; |
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27 | $lock->up; |
21 | |
28 | |
22 | =head1 DESCRIPTION |
29 | =head1 DESCRIPTION |
23 | |
30 | |
24 | This module implements coroutines. Coroutines, similar to continuations, |
31 | For a tutorial-style introduction, please read the L<Coro::Intro> |
25 | allow you to run more than one "thread of execution" in parallel. Unlike |
32 | manpage. This manpage mainly contains reference information. |
26 | threads this, only voluntary switching is used so locking problems are |
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27 | greatly reduced. |
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28 | |
33 | |
29 | Although this is the "main" module of the Coro family it provides only |
34 | This module collection manages coroutines, that is, cooperative |
30 | low-level functionality. See L<Coro::Process> and related modules for a |
35 | threads. Coroutines are similar to kernel threads but don't (in general) |
31 | more useful process abstraction including scheduling. |
36 | run in parallel at the same time even on SMP machines. The specific flavor |
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37 | of coroutine used in this module also guarantees you that it will not |
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38 | switch between coroutines unless necessary, at easily-identified points |
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39 | in your program, so locking and parallel access are rarely an issue, |
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40 | making coroutine programming much safer and easier than using other thread |
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41 | models. |
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42 | |
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43 | Unlike the so-called "Perl threads" (which are not actually real threads |
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44 | but only the windows process emulation ported to unix), Coro provides a |
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45 | full shared address space, which makes communication between coroutines |
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46 | very easy. And coroutines are fast, too: disabling the Windows process |
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47 | emulation code in your perl and using Coro can easily result in a two to |
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48 | four times speed increase for your programs. |
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49 | |
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50 | Coro achieves that by supporting multiple running interpreters that share |
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51 | data, which is especially useful to code pseudo-parallel processes and |
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52 | for event-based programming, such as multiple HTTP-GET requests running |
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53 | concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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54 | into an event-based environment. |
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55 | |
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56 | In this module, a coroutines is defined as "callchain + lexical variables |
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57 | + @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own |
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58 | callchain, its own set of lexicals and its own set of perls most important |
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59 | global variables (see L<Coro::State> for more configuration and background |
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60 | info). |
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61 | |
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62 | See also the C<SEE ALSO> section at the end of this document - the Coro |
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63 | module family is quite large. |
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64 | |
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65 | =cut |
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66 | |
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67 | package Coro; |
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68 | |
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69 | use strict qw(vars subs); |
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70 | no warnings "uninitialized"; |
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71 | |
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72 | use Coro::State; |
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73 | |
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74 | use base qw(Coro::State Exporter); |
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75 | |
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76 | our $idle; # idle handler |
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77 | our $main; # main coroutine |
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78 | our $current; # current coroutine |
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79 | |
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80 | our $VERSION = "5.0"; |
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81 | |
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82 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
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83 | our %EXPORT_TAGS = ( |
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84 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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85 | ); |
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86 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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87 | |
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88 | =head1 GLOBAL VARIABLES |
32 | |
89 | |
33 | =over 4 |
90 | =over 4 |
34 | |
91 | |
35 | =cut |
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36 | |
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37 | package Coro; |
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38 | |
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39 | BEGIN { |
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40 | $VERSION = 0.03; |
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41 | |
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42 | require XSLoader; |
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43 | XSLoader::load Coro, $VERSION; |
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44 | } |
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45 | |
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46 | =item $main |
92 | =item $Coro::main |
47 | |
93 | |
48 | This coroutine represents the main program. |
94 | This variable stores the coroutine object that represents the main |
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95 | program. While you cna C<ready> it and do most other things you can do to |
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96 | coroutines, it is mainly useful to compare again C<$Coro::current>, to see |
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97 | whether you are running in the main program or not. |
49 | |
98 | |
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99 | =cut |
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100 | |
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101 | # $main is now being initialised by Coro::State |
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102 | |
50 | =item $current |
103 | =item $Coro::current |
51 | |
104 | |
52 | The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). |
105 | The coroutine object representing the current coroutine (the last |
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106 | coroutine that the Coro scheduler switched to). The initial value is |
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107 | C<$Coro::main> (of course). |
53 | |
108 | |
54 | =cut |
109 | This variable is B<strictly> I<read-only>. You can take copies of the |
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110 | value stored in it and use it as any other coroutine object, but you must |
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111 | not otherwise modify the variable itself. |
55 | |
112 | |
56 | $main = $current = _newprocess { |
113 | =cut |
57 | # never being called |
114 | |
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115 | sub current() { $current } # [DEPRECATED] |
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116 | |
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117 | =item $Coro::idle |
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118 | |
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119 | This variable is mainly useful to integrate Coro into event loops. It is |
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120 | usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is |
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121 | pretty low-level functionality. |
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122 | |
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123 | This variable stores a callback that is called whenever the scheduler |
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124 | finds no ready coroutines to run. The default implementation prints |
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125 | "FATAL: deadlock detected" and exits, because the program has no other way |
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126 | to continue. |
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127 | |
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128 | This hook is overwritten by modules such as C<Coro::Timer> and |
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129 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
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130 | coroutine so the scheduler can run it. |
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131 | |
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132 | Note that the callback I<must not>, under any circumstances, block |
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133 | the current coroutine. Normally, this is achieved by having an "idle |
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134 | coroutine" that calls the event loop and then blocks again, and then |
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135 | readying that coroutine in the idle handler. |
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136 | |
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137 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
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138 | technique. |
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139 | |
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140 | Please note that if your callback recursively invokes perl (e.g. for event |
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141 | handlers), then it must be prepared to be called recursively itself. |
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142 | |
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143 | =cut |
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144 | |
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145 | $idle = sub { |
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146 | require Carp; |
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147 | Carp::croak ("FATAL: deadlock detected"); |
58 | }; |
148 | }; |
59 | |
149 | |
60 | =item $error, $error_msg, $error_coro |
150 | # this coroutine is necessary because a coroutine |
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151 | # cannot destroy itself. |
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152 | our @destroy; |
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153 | our $manager; |
61 | |
154 | |
62 | This coroutine will be called on fatal errors. C<$error_msg> and |
155 | $manager = new Coro sub { |
63 | C<$error_coro> return the error message and the error-causing coroutine, |
156 | while () { |
64 | respectively. |
157 | Coro::_cancel shift @destroy |
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158 | while @destroy; |
65 | |
159 | |
66 | =cut |
160 | &schedule; |
67 | |
161 | } |
68 | $error_msg = |
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69 | $error_coro = undef; |
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70 | |
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71 | $error = _newprocess { |
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72 | print STDERR "FATAL: $error_msg\nprogram aborted\n"; |
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73 | exit 250; |
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74 | }; |
162 | }; |
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163 | $manager->{desc} = "[coro manager]"; |
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164 | $manager->prio (PRIO_MAX); |
75 | |
165 | |
76 | =item $coro = new $coderef [, @args] |
166 | =back |
77 | |
167 | |
78 | Create a new coroutine and return it. The first C<resume> call to this |
168 | =head1 SIMPLE COROUTINE CREATION |
79 | coroutine will start execution at the given coderef. If it returns it |
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80 | should return a coroutine to switch to. If, after returning, the coroutine |
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81 | is C<resume>d again it starts execution again at the givne coderef. |
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82 | |
169 | |
83 | =cut |
170 | =over 4 |
84 | |
171 | |
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172 | =item async { ... } [@args...] |
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173 | |
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174 | Create a new coroutine and return it's coroutine object (usually |
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175 | unused). The coroutine will be put into the ready queue, so |
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176 | it will start running automatically on the next scheduler run. |
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177 | |
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178 | The first argument is a codeblock/closure that should be executed in the |
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179 | coroutine. When it returns argument returns the coroutine is automatically |
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180 | terminated. |
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181 | |
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182 | The remaining arguments are passed as arguments to the closure. |
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183 | |
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184 | See the C<Coro::State::new> constructor for info about the coroutine |
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185 | environment in which coroutines are executed. |
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186 | |
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187 | Calling C<exit> in a coroutine will do the same as calling exit outside |
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188 | the coroutine. Likewise, when the coroutine dies, the program will exit, |
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189 | just as it would in the main program. |
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190 | |
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191 | If you do not want that, you can provide a default C<die> handler, or |
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192 | simply avoid dieing (by use of C<eval>). |
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193 | |
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194 | Example: Create a new coroutine that just prints its arguments. |
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195 | |
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196 | async { |
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197 | print "@_\n"; |
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198 | } 1,2,3,4; |
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199 | |
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200 | =cut |
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201 | |
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202 | sub async(&@) { |
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203 | my $coro = new Coro @_; |
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204 | $coro->ready; |
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205 | $coro |
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206 | } |
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207 | |
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208 | =item async_pool { ... } [@args...] |
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209 | |
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210 | Similar to C<async>, but uses a coroutine pool, so you should not call |
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211 | terminate or join on it (although you are allowed to), and you get a |
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212 | coroutine that might have executed other code already (which can be good |
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213 | or bad :). |
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214 | |
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215 | On the plus side, this function is about twice as fast as creating (and |
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216 | destroying) a completely new coroutine, so if you need a lot of generic |
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217 | coroutines in quick successsion, use C<async_pool>, not C<async>. |
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218 | |
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219 | The code block is executed in an C<eval> context and a warning will be |
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220 | issued in case of an exception instead of terminating the program, as |
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221 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
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222 | will not work in the expected way, unless you call terminate or cancel, |
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223 | which somehow defeats the purpose of pooling (but is fine in the |
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224 | exceptional case). |
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225 | |
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226 | The priority will be reset to C<0> after each run, tracing will be |
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227 | disabled, the description will be reset and the default output filehandle |
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228 | gets restored, so you can change all these. Otherwise the coroutine will |
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229 | be re-used "as-is": most notably if you change other per-coroutine global |
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230 | stuff such as C<$/> you I<must needs> revert that change, which is most |
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231 | simply done by using local as in: C<< local $/ >>. |
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232 | |
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233 | The idle pool size is limited to C<8> idle coroutines (this can be |
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234 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
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235 | coros as required. |
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236 | |
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237 | If you are concerned about pooled coroutines growing a lot because a |
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238 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
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239 | { terminate }> once per second or so to slowly replenish the pool. In |
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240 | addition to that, when the stacks used by a handler grows larger than 32kb |
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241 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
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242 | |
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243 | =cut |
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244 | |
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245 | our $POOL_SIZE = 8; |
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246 | our $POOL_RSS = 32 * 1024; |
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247 | our @async_pool; |
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248 | |
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249 | sub pool_handler { |
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250 | while () { |
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251 | eval { |
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252 | &{&_pool_handler} while 1; |
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253 | }; |
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254 | |
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255 | warn $@ if $@; |
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256 | } |
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257 | } |
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258 | |
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259 | =back |
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260 | |
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261 | =head1 STATIC METHODS |
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262 | |
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263 | Static methods are actually functions that implicitly operate on the |
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264 | current coroutine. |
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265 | |
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266 | =over 4 |
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267 | |
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268 | =item schedule |
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269 | |
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270 | Calls the scheduler. The scheduler will find the next coroutine that is |
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271 | to be run from the ready queue and switches to it. The next coroutine |
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272 | to be run is simply the one with the highest priority that is longest |
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273 | in its ready queue. If there is no coroutine ready, it will clal the |
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274 | C<$Coro::idle> hook. |
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275 | |
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276 | Please note that the current coroutine will I<not> be put into the ready |
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277 | queue, so calling this function usually means you will never be called |
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278 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
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279 | thus waking you up. |
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280 | |
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281 | This makes C<schedule> I<the> generic method to use to block the current |
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282 | coroutine and wait for events: first you remember the current coroutine in |
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283 | a variable, then arrange for some callback of yours to call C<< ->ready |
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284 | >> on that once some event happens, and last you call C<schedule> to put |
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285 | yourself to sleep. Note that a lot of things can wake your coroutine up, |
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286 | so you need to check whether the event indeed happened, e.g. by storing the |
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287 | status in a variable. |
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288 | |
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289 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
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290 | |
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291 | =item cede |
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292 | |
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293 | "Cede" to other coroutines. This function puts the current coroutine into |
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294 | the ready queue and calls C<schedule>, which has the effect of giving |
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295 | up the current "timeslice" to other coroutines of the same or higher |
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296 | priority. Once your coroutine gets its turn again it will automatically be |
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297 | resumed. |
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298 | |
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299 | This function is often called C<yield> in other languages. |
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300 | |
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301 | =item Coro::cede_notself |
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302 | |
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303 | Works like cede, but is not exported by default and will cede to I<any> |
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304 | coroutine, regardless of priority. This is useful sometimes to ensure |
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305 | progress is made. |
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306 | |
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307 | =item terminate [arg...] |
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308 | |
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309 | Terminates the current coroutine with the given status values (see L<cancel>). |
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310 | |
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311 | =item killall |
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312 | |
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313 | Kills/terminates/cancels all coroutines except the currently running |
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314 | one. This is useful after a fork, either in the child or the parent, as |
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315 | usually only one of them should inherit the running coroutines. |
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316 | |
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317 | Note that while this will try to free some of the main programs resources, |
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318 | you cannot free all of them, so if a coroutine that is not the main |
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319 | program calls this function, there will be some one-time resource leak. |
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320 | |
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321 | =cut |
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322 | |
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323 | sub killall { |
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324 | for (Coro::State::list) { |
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325 | $_->cancel |
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326 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
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327 | } |
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328 | } |
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329 | |
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330 | =back |
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331 | |
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332 | =head1 COROUTINE OBJECT METHODS |
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333 | |
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334 | These are the methods you can call on coroutine objects (or to create |
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335 | them). |
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336 | |
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337 | =over 4 |
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338 | |
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339 | =item new Coro \&sub [, @args...] |
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340 | |
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341 | Create a new coroutine and return it. When the sub returns, the coroutine |
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342 | automatically terminates as if C<terminate> with the returned values were |
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343 | called. To make the coroutine run you must first put it into the ready |
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344 | queue by calling the ready method. |
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345 | |
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346 | See C<async> and C<Coro::State::new> for additional info about the |
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347 | coroutine environment. |
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348 | |
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349 | =cut |
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350 | |
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351 | sub _terminate { |
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352 | terminate &{+shift}; |
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353 | } |
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354 | |
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355 | =item $success = $coroutine->ready |
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356 | |
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357 | Put the given coroutine into the end of its ready queue (there is one |
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358 | queue for each priority) and return true. If the coroutine is already in |
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359 | the ready queue, do nothing and return false. |
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360 | |
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361 | This ensures that the scheduler will resume this coroutine automatically |
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362 | once all the coroutines of higher priority and all coroutines of the same |
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363 | priority that were put into the ready queue earlier have been resumed. |
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364 | |
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365 | =item $is_ready = $coroutine->is_ready |
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366 | |
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367 | Return whether the coroutine is currently the ready queue or not, |
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368 | |
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369 | =item $coroutine->cancel (arg...) |
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370 | |
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371 | Terminates the given coroutine and makes it return the given arguments as |
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372 | status (default: the empty list). Never returns if the coroutine is the |
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373 | current coroutine. |
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374 | |
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375 | =cut |
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376 | |
85 | sub new { |
377 | sub cancel { |
86 | my $class = $_[0]; |
378 | my $self = shift; |
87 | my $proc = $_[1]; |
379 | |
88 | bless _newprocess { |
380 | if ($current == $self) { |
89 | do { |
381 | terminate @_; |
90 | eval { &$proc->resume }; |
382 | } else { |
91 | if ($@) { |
383 | $self->{_status} = [@_]; |
92 | ($error_msg, $error_coro) = ($@, $current); |
384 | $self->_cancel; |
93 | $error->resume; |
385 | } |
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386 | } |
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387 | |
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388 | =item $coroutine->schedule_to |
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389 | |
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390 | Puts the current coroutine to sleep (like C<Coro::schedule>), but instead |
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391 | of continuing with the next coro from the ready queue, always switch to |
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392 | the given coroutine object (regardless of priority etc.). The readyness |
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393 | state of that coroutine isn't changed. |
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394 | |
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395 | This is an advanced method for special cases - I'd love to hear about any |
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396 | uses for this one. |
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397 | |
|
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398 | =item $coroutine->cede_to |
|
|
399 | |
|
|
400 | Like C<schedule_to>, but puts the current coroutine into the ready |
|
|
401 | queue. This has the effect of temporarily switching to the given |
|
|
402 | coroutine, and continuing some time later. |
|
|
403 | |
|
|
404 | This is an advanced method for special cases - I'd love to hear about any |
|
|
405 | uses for this one. |
|
|
406 | |
|
|
407 | =item $coroutine->throw ([$scalar]) |
|
|
408 | |
|
|
409 | If C<$throw> is specified and defined, it will be thrown as an exception |
|
|
410 | inside the coroutine at the next convenient point in time. Otherwise |
|
|
411 | clears the exception object. |
|
|
412 | |
|
|
413 | Coro will check for the exception each time a schedule-like-function |
|
|
414 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
|
|
415 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
|
|
416 | detect this case and return early in case an exception is pending. |
|
|
417 | |
|
|
418 | The exception object will be thrown "as is" with the specified scalar in |
|
|
419 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
|
|
420 | (unlike with C<die>). |
|
|
421 | |
|
|
422 | This can be used as a softer means than C<cancel> to ask a coroutine to |
|
|
423 | end itself, although there is no guarantee that the exception will lead to |
|
|
424 | termination, and if the exception isn't caught it might well end the whole |
|
|
425 | program. |
|
|
426 | |
|
|
427 | You might also think of C<throw> as being the moral equivalent of |
|
|
428 | C<kill>ing a coroutine with a signal (in this case, a scalar). |
|
|
429 | |
|
|
430 | =item $coroutine->join |
|
|
431 | |
|
|
432 | Wait until the coroutine terminates and return any values given to the |
|
|
433 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
|
|
434 | from multiple coroutines, and all will be resumed and given the status |
|
|
435 | return once the C<$coroutine> terminates. |
|
|
436 | |
|
|
437 | =cut |
|
|
438 | |
|
|
439 | sub join { |
|
|
440 | my $self = shift; |
|
|
441 | |
|
|
442 | unless ($self->{_status}) { |
|
|
443 | my $current = $current; |
|
|
444 | |
|
|
445 | push @{$self->{_on_destroy}}, sub { |
|
|
446 | $current->ready; |
|
|
447 | undef $current; |
|
|
448 | }; |
|
|
449 | |
|
|
450 | &schedule while $current; |
|
|
451 | } |
|
|
452 | |
|
|
453 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
454 | } |
|
|
455 | |
|
|
456 | =item $coroutine->on_destroy (\&cb) |
|
|
457 | |
|
|
458 | Registers a callback that is called when this coroutine gets destroyed, |
|
|
459 | but before it is joined. The callback gets passed the terminate arguments, |
|
|
460 | if any, and I<must not> die, under any circumstances. |
|
|
461 | |
|
|
462 | =cut |
|
|
463 | |
|
|
464 | sub on_destroy { |
|
|
465 | my ($self, $cb) = @_; |
|
|
466 | |
|
|
467 | push @{ $self->{_on_destroy} }, $cb; |
|
|
468 | } |
|
|
469 | |
|
|
470 | =item $oldprio = $coroutine->prio ($newprio) |
|
|
471 | |
|
|
472 | Sets (or gets, if the argument is missing) the priority of the |
|
|
473 | coroutine. Higher priority coroutines get run before lower priority |
|
|
474 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
|
|
475 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
|
|
476 | to get then): |
|
|
477 | |
|
|
478 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
|
|
479 | 3 > 1 > 0 > -1 > -3 > -4 |
|
|
480 | |
|
|
481 | # set priority to HIGH |
|
|
482 | current->prio(PRIO_HIGH); |
|
|
483 | |
|
|
484 | The idle coroutine ($Coro::idle) always has a lower priority than any |
|
|
485 | existing coroutine. |
|
|
486 | |
|
|
487 | Changing the priority of the current coroutine will take effect immediately, |
|
|
488 | but changing the priority of coroutines in the ready queue (but not |
|
|
489 | running) will only take effect after the next schedule (of that |
|
|
490 | coroutine). This is a bug that will be fixed in some future version. |
|
|
491 | |
|
|
492 | =item $newprio = $coroutine->nice ($change) |
|
|
493 | |
|
|
494 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
|
|
495 | higher values mean lower priority, just as in unix). |
|
|
496 | |
|
|
497 | =item $olddesc = $coroutine->desc ($newdesc) |
|
|
498 | |
|
|
499 | Sets (or gets in case the argument is missing) the description for this |
|
|
500 | coroutine. This is just a free-form string you can associate with a |
|
|
501 | coroutine. |
|
|
502 | |
|
|
503 | This method simply sets the C<< $coroutine->{desc} >> member to the given |
|
|
504 | string. You can modify this member directly if you wish. |
|
|
505 | |
|
|
506 | =cut |
|
|
507 | |
|
|
508 | sub desc { |
|
|
509 | my $old = $_[0]{desc}; |
|
|
510 | $_[0]{desc} = $_[1] if @_ > 1; |
|
|
511 | $old; |
|
|
512 | } |
|
|
513 | |
|
|
514 | sub transfer { |
|
|
515 | require Carp; |
|
|
516 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
517 | } |
|
|
518 | |
|
|
519 | =back |
|
|
520 | |
|
|
521 | =head1 GLOBAL FUNCTIONS |
|
|
522 | |
|
|
523 | =over 4 |
|
|
524 | |
|
|
525 | =item Coro::nready |
|
|
526 | |
|
|
527 | Returns the number of coroutines that are currently in the ready state, |
|
|
528 | i.e. that can be switched to by calling C<schedule> directory or |
|
|
529 | indirectly. The value C<0> means that the only runnable coroutine is the |
|
|
530 | currently running one, so C<cede> would have no effect, and C<schedule> |
|
|
531 | would cause a deadlock unless there is an idle handler that wakes up some |
|
|
532 | coroutines. |
|
|
533 | |
|
|
534 | =item my $guard = Coro::guard { ... } |
|
|
535 | |
|
|
536 | This creates and returns a guard object. Nothing happens until the object |
|
|
537 | gets destroyed, in which case the codeblock given as argument will be |
|
|
538 | executed. This is useful to free locks or other resources in case of a |
|
|
539 | runtime error or when the coroutine gets canceled, as in both cases the |
|
|
540 | guard block will be executed. The guard object supports only one method, |
|
|
541 | C<< ->cancel >>, which will keep the codeblock from being executed. |
|
|
542 | |
|
|
543 | Example: set some flag and clear it again when the coroutine gets canceled |
|
|
544 | or the function returns: |
|
|
545 | |
|
|
546 | sub do_something { |
|
|
547 | my $guard = Coro::guard { $busy = 0 }; |
|
|
548 | $busy = 1; |
|
|
549 | |
|
|
550 | # do something that requires $busy to be true |
|
|
551 | } |
|
|
552 | |
|
|
553 | =cut |
|
|
554 | |
|
|
555 | sub guard(&) { |
|
|
556 | bless \(my $cb = $_[0]), "Coro::guard" |
|
|
557 | } |
|
|
558 | |
|
|
559 | sub Coro::guard::cancel { |
|
|
560 | ${$_[0]} = sub { }; |
|
|
561 | } |
|
|
562 | |
|
|
563 | sub Coro::guard::DESTROY { |
|
|
564 | ${$_[0]}->(); |
|
|
565 | } |
|
|
566 | |
|
|
567 | |
|
|
568 | =item unblock_sub { ... } |
|
|
569 | |
|
|
570 | This utility function takes a BLOCK or code reference and "unblocks" it, |
|
|
571 | returning a new coderef. Unblocking means that calling the new coderef |
|
|
572 | will return immediately without blocking, returning nothing, while the |
|
|
573 | original code ref will be called (with parameters) from within another |
|
|
574 | coroutine. |
|
|
575 | |
|
|
576 | The reason this function exists is that many event libraries (such as the |
|
|
577 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
|
|
578 | of thread-safety). This means you must not block within event callbacks, |
|
|
579 | otherwise you might suffer from crashes or worse. The only event library |
|
|
580 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
|
|
581 | |
|
|
582 | This function allows your callbacks to block by executing them in another |
|
|
583 | coroutine where it is safe to block. One example where blocking is handy |
|
|
584 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
|
|
585 | disk, for example. |
|
|
586 | |
|
|
587 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
|
|
588 | creating event callbacks that want to block. |
|
|
589 | |
|
|
590 | If your handler does not plan to block (e.g. simply sends a message to |
|
|
591 | another coroutine, or puts some other coroutine into the ready queue), |
|
|
592 | there is no reason to use C<unblock_sub>. |
|
|
593 | |
|
|
594 | Note that you also need to use C<unblock_sub> for any other callbacks that |
|
|
595 | are indirectly executed by any C-based event loop. For example, when you |
|
|
596 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
|
|
597 | provides callbacks that are the result of some event callback, then you |
|
|
598 | must not block either, or use C<unblock_sub>. |
|
|
599 | |
|
|
600 | =cut |
|
|
601 | |
|
|
602 | our @unblock_queue; |
|
|
603 | |
|
|
604 | # we create a special coro because we want to cede, |
|
|
605 | # to reduce pressure on the coro pool (because most callbacks |
|
|
606 | # return immediately and can be reused) and because we cannot cede |
|
|
607 | # inside an event callback. |
|
|
608 | our $unblock_scheduler = new Coro sub { |
|
|
609 | while () { |
|
|
610 | while (my $cb = pop @unblock_queue) { |
|
|
611 | &async_pool (@$cb); |
|
|
612 | |
|
|
613 | # for short-lived callbacks, this reduces pressure on the coro pool |
|
|
614 | # as the chance is very high that the async_poll coro will be back |
|
|
615 | # in the idle state when cede returns |
|
|
616 | cede; |
94 | } |
617 | } |
95 | } while (1); |
618 | schedule; # sleep well |
96 | }, $class; |
619 | } |
97 | } |
620 | }; |
|
|
621 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
98 | |
622 | |
99 | =item $coro->resume |
623 | sub unblock_sub(&) { |
|
|
624 | my $cb = shift; |
100 | |
625 | |
101 | Resume execution at the given coroutine. |
626 | sub { |
102 | |
627 | unshift @unblock_queue, [$cb, @_]; |
103 | =cut |
628 | $unblock_scheduler->ready; |
104 | |
629 | } |
105 | my $prev; |
|
|
106 | |
|
|
107 | # I call the _transfer function from a pelr function |
|
|
108 | # because that way perl saves all important things on |
|
|
109 | # the stack. |
|
|
110 | sub resume { |
|
|
111 | $prev = $current; $current = $_[0]; |
|
|
112 | _transfer($prev, $current); |
|
|
113 | } |
630 | } |
|
|
631 | |
|
|
632 | =item $cb = Coro::rouse_cb |
|
|
633 | |
|
|
634 | Create and return a "rouse callback". That's a code reference that, when |
|
|
635 | called, will save its arguments and notify the owner coroutine of the |
|
|
636 | callback. |
|
|
637 | |
|
|
638 | See the next function. |
|
|
639 | |
|
|
640 | =item @args = Coro::rouse_wait [$cb] |
|
|
641 | |
|
|
642 | Wait for the specified rouse callback (or the last one tht was created in |
|
|
643 | this coroutine). |
|
|
644 | |
|
|
645 | As soon as the callback is invoked (or when the calback was invoked before |
|
|
646 | C<rouse_wait>), it will return a copy of the arguments originally passed |
|
|
647 | to the rouse callback. |
|
|
648 | |
|
|
649 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
|
|
650 | |
|
|
651 | =back |
|
|
652 | |
|
|
653 | =cut |
114 | |
654 | |
115 | 1; |
655 | 1; |
116 | |
656 | |
|
|
657 | =head1 HOW TO WAIT FOR A CALLBACK |
|
|
658 | |
|
|
659 | It is very common for a coroutine to wait for some callback to be |
|
|
660 | called. This occurs naturally when you use coroutines in an otherwise |
|
|
661 | event-based program, or when you use event-based libraries. |
|
|
662 | |
|
|
663 | These typically register a callback for some event, and call that callback |
|
|
664 | when the event occured. In a coroutine, however, you typically want to |
|
|
665 | just wait for the event, simplyifying things. |
|
|
666 | |
|
|
667 | For example C<< AnyEvent->child >> registers a callback to be called when |
|
|
668 | a specific child has exited: |
|
|
669 | |
|
|
670 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
671 | |
|
|
672 | But from withina coroutine, you often just want to write this: |
|
|
673 | |
|
|
674 | my $status = wait_for_child $pid; |
|
|
675 | |
|
|
676 | Coro offers two functions specifically designed to make this easy, |
|
|
677 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
|
|
678 | |
|
|
679 | The first function, C<rouse_cb>, generates and returns a callback that, |
|
|
680 | when invoked, will save it's arguments and notify the coroutine that |
|
|
681 | created the callback. |
|
|
682 | |
|
|
683 | The second function, C<rouse_wait>, waits for the callback to be called |
|
|
684 | (by calling C<schedule> to go to sleep) and returns the arguments |
|
|
685 | originally passed to the callback. |
|
|
686 | |
|
|
687 | Using these functions, it becomes easy to write the C<wait_for_child> |
|
|
688 | function mentioned above: |
|
|
689 | |
|
|
690 | sub wait_for_child($) { |
|
|
691 | my ($pid) = @_; |
|
|
692 | |
|
|
693 | my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
|
|
694 | |
|
|
695 | my ($rpid, $rstatus) = Coro::rouse_wait; |
|
|
696 | $rstatus |
|
|
697 | } |
|
|
698 | |
|
|
699 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
|
|
700 | you can roll your own, using C<schedule>: |
|
|
701 | |
|
|
702 | sub wait_for_child($) { |
|
|
703 | my ($pid) = @_; |
|
|
704 | |
|
|
705 | # store the current coroutine in $current, |
|
|
706 | # and provide result variables for the closure passed to ->child |
|
|
707 | my $current = $Coro::current; |
|
|
708 | my ($done, $rstatus); |
|
|
709 | |
|
|
710 | # pass a closure to ->child |
|
|
711 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
712 | $rstatus = $_[1]; # remember rstatus |
|
|
713 | $done = 1; # mark $rstatus as valud |
|
|
714 | }); |
|
|
715 | |
|
|
716 | # wait until the closure has been called |
|
|
717 | schedule while !$done; |
|
|
718 | |
|
|
719 | $rstatus |
|
|
720 | } |
|
|
721 | |
|
|
722 | |
|
|
723 | =head1 BUGS/LIMITATIONS |
|
|
724 | |
|
|
725 | =over 4 |
|
|
726 | |
|
|
727 | =item fork with pthread backend |
|
|
728 | |
|
|
729 | When Coro is compiled using the pthread backend (which isn't recommended |
|
|
730 | but required on many BSDs as their libcs are completely broken), then |
|
|
731 | coroutines will not survive a fork. There is no known workaround except to |
|
|
732 | fix your libc and use a saner backend. |
|
|
733 | |
|
|
734 | =item perl process emulation ("threads") |
|
|
735 | |
|
|
736 | This module is not perl-pseudo-thread-safe. You should only ever use this |
|
|
737 | module from the same thread (this requirement might be removed in the |
|
|
738 | future to allow per-thread schedulers, but Coro::State does not yet allow |
|
|
739 | this). I recommend disabling thread support and using processes, as having |
|
|
740 | the windows process emulation enabled under unix roughly halves perl |
|
|
741 | performance, even when not used. |
|
|
742 | |
|
|
743 | =item coroutine switching not signal safe |
|
|
744 | |
|
|
745 | You must not switch to another coroutine from within a signal handler |
|
|
746 | (only relevant with %SIG - most event libraries provide safe signals). |
|
|
747 | |
|
|
748 | That means you I<MUST NOT> call any function that might "block" the |
|
|
749 | current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
|
|
750 | anything that calls those. Everything else, including calling C<ready>, |
|
|
751 | works. |
|
|
752 | |
117 | =back |
753 | =back |
118 | |
754 | |
119 | =head1 BUGS |
|
|
120 | |
|
|
121 | This module has not yet been extensively tested. |
|
|
122 | |
755 | |
123 | =head1 SEE ALSO |
756 | =head1 SEE ALSO |
124 | |
757 | |
125 | L<Coro::Process>, L<Coro::Signal>. |
758 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
|
|
759 | |
|
|
760 | Debugging: L<Coro::Debug>. |
|
|
761 | |
|
|
762 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
|
|
763 | |
|
|
764 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
765 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
|
|
766 | |
|
|
767 | IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
|
|
768 | |
|
|
769 | Compatibility: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
770 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
771 | L<Coro::Select>. |
|
|
772 | |
|
|
773 | XS API: L<Coro::MakeMaker>. |
|
|
774 | |
|
|
775 | Low level Configuration, Coroutine Environment: L<Coro::State>. |
126 | |
776 | |
127 | =head1 AUTHOR |
777 | =head1 AUTHOR |
128 | |
778 | |
129 | Marc Lehmann <pcg@goof.com> |
779 | Marc Lehmann <schmorp@schmorp.de> |
130 | http://www.goof.com/pcg/marc/ |
780 | http://home.schmorp.de/ |
131 | |
781 | |
132 | =cut |
782 | =cut |
133 | |
783 | |