1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - create and manage simple coroutines |
3 | Coro - coroutine process abstraction |
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 | $new->transfer($main); |
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12 | print "in coroutine again, switching back\n"; |
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13 | $new->transfer($main); |
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14 | }; |
11 | }; |
15 | |
12 | |
16 | $main = new Coro; |
13 | # alternatively create an async coroutine like this: |
17 | |
14 | |
18 | print "in main, switching to coroutine\n"; |
15 | sub some_func : Coro { |
19 | $main->transfer($new); |
16 | # some more async code |
20 | print "back in main, switch to coroutine again\n"; |
17 | } |
21 | $main->transfer($new); |
18 | |
22 | print "back in main\n"; |
19 | cede; |
23 | |
20 | |
24 | =head1 DESCRIPTION |
21 | =head1 DESCRIPTION |
25 | |
22 | |
26 | This module implements coroutines. Coroutines, similar to continuations, |
23 | This module collection manages coroutines. Coroutines are similar |
27 | allow you to run more than one "thread of execution" in parallel. Unlike |
24 | to threads but don't run in parallel at the same time even on SMP |
28 | threads this, only voluntary switching is used so locking problems are |
25 | machines. The specific flavor of coroutine use din this module also |
29 | greatly reduced. |
26 | guarentees you that it will not switch between coroutines unless |
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27 | necessary, at easily-identified points in your program, so locking and |
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28 | parallel access are rarely an issue, making coroutine programming much |
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29 | safer than threads programming. |
30 | |
30 | |
31 | Although this is the "main" module of the Coro family it provides only |
31 | (Perl, however, does not natively support real threads but instead does a |
32 | low-level functionality. See L<Coro::Process> and related modules for a |
32 | very slow and memory-intensive emulation of processes using threads. This |
33 | more useful process abstraction including scheduling. |
33 | is a performance win on Windows machines, and a loss everywhere else). |
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34 | |
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35 | In this module, coroutines are defined as "callchain + lexical variables + |
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36 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
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37 | its own set of lexicals and its own set of perls most important global |
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38 | variables. |
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39 | |
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40 | =cut |
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41 | |
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42 | package Coro; |
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43 | |
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44 | use strict; |
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45 | no warnings "uninitialized"; |
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46 | |
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47 | use Coro::State; |
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48 | |
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49 | use base qw(Coro::State Exporter); |
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50 | |
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51 | our $idle; # idle handler |
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52 | our $main; # main coroutine |
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53 | our $current; # current coroutine |
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54 | |
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55 | our $VERSION = '3.11'; |
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56 | |
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57 | our @EXPORT = qw(async cede schedule terminate current unblock_sub); |
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58 | our %EXPORT_TAGS = ( |
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59 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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60 | ); |
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61 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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62 | |
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63 | { |
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64 | my @async; |
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65 | my $init; |
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66 | |
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67 | # this way of handling attributes simply is NOT scalable ;() |
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68 | sub import { |
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69 | no strict 'refs'; |
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70 | |
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71 | Coro->export_to_level (1, @_); |
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72 | |
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73 | my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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74 | *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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75 | my ($package, $ref) = (shift, shift); |
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76 | my @attrs; |
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77 | for (@_) { |
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78 | if ($_ eq "Coro") { |
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79 | push @async, $ref; |
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80 | unless ($init++) { |
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81 | eval q{ |
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82 | sub INIT { |
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83 | &async(pop @async) while @async; |
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84 | } |
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85 | }; |
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86 | } |
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87 | } else { |
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88 | push @attrs, $_; |
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89 | } |
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90 | } |
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91 | return $old ? $old->($package, $ref, @attrs) : @attrs; |
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92 | }; |
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93 | } |
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94 | |
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95 | } |
34 | |
96 | |
35 | =over 4 |
97 | =over 4 |
36 | |
98 | |
37 | =cut |
99 | =item $main |
38 | |
100 | |
39 | package Coro; |
101 | This coroutine represents the main program. |
40 | |
102 | |
41 | BEGIN { |
103 | =cut |
42 | $VERSION = 0.03; |
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43 | |
104 | |
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105 | $main = new Coro; |
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106 | |
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107 | =item $current (or as function: current) |
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108 | |
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109 | The current coroutine (the last coroutine switched to). The initial value |
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110 | is C<$main> (of course). |
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111 | |
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112 | This variable is B<strictly> I<read-only>. It is provided for performance |
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113 | reasons. If performance is not essentiel you are encouraged to use the |
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114 | C<Coro::current> function instead. |
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115 | |
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116 | =cut |
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117 | |
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118 | # maybe some other module used Coro::Specific before... |
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119 | $main->{specific} = $current->{specific} |
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120 | if $current; |
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121 | |
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122 | _set_current $main; |
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123 | |
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124 | sub current() { $current } |
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125 | |
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126 | =item $idle |
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127 | |
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128 | A callback that is called whenever the scheduler finds no ready coroutines |
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129 | to run. The default implementation prints "FATAL: deadlock detected" and |
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130 | exits, because the program has no other way to continue. |
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131 | |
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132 | This hook is overwritten by modules such as C<Coro::Timer> and |
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133 | C<Coro::Event> to wait on an external event that hopefully wake up a |
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134 | coroutine so the scheduler can run it. |
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135 | |
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136 | Please note that if your callback recursively invokes perl (e.g. for event |
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137 | handlers), then it must be prepared to be called recursively. |
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138 | |
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139 | =cut |
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140 | |
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141 | $idle = sub { |
44 | require XSLoader; |
142 | require Carp; |
45 | XSLoader::load Coro, $VERSION; |
143 | Carp::croak ("FATAL: deadlock detected"); |
46 | } |
144 | }; |
47 | |
145 | |
48 | =item $coro = new [$coderef [, @args]] |
146 | # this coroutine is necessary because a coroutine |
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147 | # cannot destroy itself. |
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148 | my @destroy; |
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149 | my $manager; $manager = new Coro sub { |
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150 | while () { |
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151 | # by overwriting the state object with the manager we destroy it |
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152 | # while still being able to schedule this coroutine (in case it has |
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153 | # been readied multiple times. this is harmless since the manager |
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154 | # can be called as many times as neccessary and will always |
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155 | # remove itself from the runqueue |
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156 | while (@destroy) { |
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157 | my $coro = pop @destroy; |
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158 | $coro->{status} ||= []; |
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159 | $_->ready for @{delete $coro->{join} || []}; |
49 | |
160 | |
50 | Create a new coroutine and return it. The first C<transfer> call to this |
161 | # the next line destroys the coro state, but keeps the |
51 | coroutine will start execution at the given coderef. If, the subroutine |
162 | # coroutine itself intact (we basically make it a zombie |
52 | returns it will be executed again. |
163 | # coroutine that always runs the manager thread, so it's possible |
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164 | # to transfer() to this coroutine). |
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165 | $coro->_clone_state_from ($manager); |
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166 | } |
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167 | &schedule; |
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168 | } |
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169 | }; |
53 | |
170 | |
54 | If the coderef is omitted this function will create a new "empty" |
171 | # static methods. not really. |
55 | coroutine, i.e. a coroutine that cannot be transfered to but can be used |
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56 | to save the current coroutine in. |
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57 | |
172 | |
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173 | =back |
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174 | |
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175 | =head2 STATIC METHODS |
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176 | |
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177 | Static methods are actually functions that operate on the current coroutine only. |
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178 | |
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179 | =over 4 |
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180 | |
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181 | =item async { ... } [@args...] |
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182 | |
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183 | Create a new asynchronous coroutine and return it's coroutine object |
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184 | (usually unused). When the sub returns the new coroutine is automatically |
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185 | terminated. |
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186 | |
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187 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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188 | |
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189 | When the coroutine dies, the program will exit, just as in the main |
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190 | program. |
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191 | |
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192 | # create a new coroutine that just prints its arguments |
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193 | async { |
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194 | print "@_\n"; |
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195 | } 1,2,3,4; |
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196 | |
58 | =cut |
197 | =cut |
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198 | |
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199 | sub async(&@) { |
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200 | my $pid = new Coro @_; |
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201 | $pid->ready; |
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202 | $pid |
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203 | } |
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204 | |
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205 | =item schedule |
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206 | |
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207 | Calls the scheduler. Please note that the current coroutine will not be put |
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208 | into the ready queue, so calling this function usually means you will |
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209 | never be called again unless something else (e.g. an event handler) calls |
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210 | ready. |
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211 | |
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212 | The canonical way to wait on external events is this: |
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213 | |
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214 | { |
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215 | # remember current coroutine |
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216 | my $current = $Coro::current; |
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217 | |
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218 | # register a hypothetical event handler |
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219 | on_event_invoke sub { |
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220 | # wake up sleeping coroutine |
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221 | $current->ready; |
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222 | undef $current; |
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223 | }; |
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224 | |
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225 | # call schedule until event occured. |
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226 | # in case we are woken up for other reasons |
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227 | # (current still defined), loop. |
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228 | Coro::schedule while $current; |
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229 | } |
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230 | |
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231 | =item cede |
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232 | |
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233 | "Cede" to other coroutines. This function puts the current coroutine into the |
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234 | ready queue and calls C<schedule>, which has the effect of giving up the |
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235 | current "timeslice" to other coroutines of the same or higher priority. |
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236 | |
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237 | =item terminate [arg...] |
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238 | |
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239 | Terminates the current coroutine with the given status values (see L<cancel>). |
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240 | |
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241 | =cut |
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242 | |
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243 | sub terminate { |
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244 | $current->cancel (@_); |
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245 | } |
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246 | |
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247 | =back |
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248 | |
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249 | # dynamic methods |
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250 | |
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251 | =head2 COROUTINE METHODS |
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252 | |
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253 | These are the methods you can call on coroutine objects. |
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254 | |
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255 | =over 4 |
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256 | |
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257 | =item new Coro \&sub [, @args...] |
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258 | |
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259 | Create a new coroutine and return it. When the sub returns the coroutine |
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260 | automatically terminates as if C<terminate> with the returned values were |
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261 | called. To make the coroutine run you must first put it into the ready queue |
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262 | by calling the ready method. |
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263 | |
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264 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
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265 | |
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266 | =cut |
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267 | |
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268 | sub _run_coro { |
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269 | terminate &{+shift}; |
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270 | } |
59 | |
271 | |
60 | sub new { |
272 | sub new { |
61 | my $class = $_[0]; |
273 | my $class = shift; |
62 | my $proc = $_[1] || sub { die "tried to transfer to an empty coroutine" }; |
274 | |
63 | bless _newprocess { |
275 | $class->SUPER::new (\&_run_coro, @_) |
64 | do { |
276 | } |
65 | eval { &$proc }; |
277 | |
66 | if ($@) { |
278 | =item $success = $coroutine->ready |
67 | $error_msg = $@; |
279 | |
68 | $error_coro = _newprocess { }; |
280 | Put the given coroutine into the ready queue (according to it's priority) |
69 | &transfer($error_coro, $error); |
281 | and return true. If the coroutine is already in the ready queue, do nothing |
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282 | and return false. |
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283 | |
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284 | =item $is_ready = $coroutine->is_ready |
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285 | |
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286 | Return wether the coroutine is currently the ready queue or not, |
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287 | |
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288 | =item $coroutine->cancel (arg...) |
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289 | |
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290 | Terminates the given coroutine and makes it return the given arguments as |
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291 | status (default: the empty list). |
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292 | |
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293 | =cut |
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294 | |
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295 | sub cancel { |
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296 | my $self = shift; |
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297 | $self->{status} = [@_]; |
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298 | push @destroy, $self; |
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299 | $manager->ready; |
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300 | &schedule if $current == $self; |
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301 | } |
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302 | |
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303 | =item $coroutine->join |
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304 | |
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305 | Wait until the coroutine terminates and return any values given to the |
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306 | C<terminate> or C<cancel> functions. C<join> can be called multiple times |
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307 | from multiple coroutine. |
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308 | |
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309 | =cut |
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310 | |
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311 | sub join { |
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312 | my $self = shift; |
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313 | unless ($self->{status}) { |
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314 | push @{$self->{join}}, $current; |
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315 | &schedule; |
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316 | } |
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317 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
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318 | } |
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319 | |
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320 | =item $oldprio = $coroutine->prio ($newprio) |
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321 | |
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322 | Sets (or gets, if the argument is missing) the priority of the |
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323 | coroutine. Higher priority coroutines get run before lower priority |
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324 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
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325 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
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326 | to get then): |
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327 | |
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328 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
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329 | 3 > 1 > 0 > -1 > -3 > -4 |
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330 | |
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331 | # set priority to HIGH |
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332 | current->prio(PRIO_HIGH); |
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333 | |
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334 | The idle coroutine ($Coro::idle) always has a lower priority than any |
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335 | existing coroutine. |
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336 | |
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337 | Changing the priority of the current coroutine will take effect immediately, |
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338 | but changing the priority of coroutines in the ready queue (but not |
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339 | running) will only take effect after the next schedule (of that |
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340 | coroutine). This is a bug that will be fixed in some future version. |
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341 | |
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342 | =item $newprio = $coroutine->nice ($change) |
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343 | |
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344 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
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345 | higher values mean lower priority, just as in unix). |
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346 | |
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347 | =item $olddesc = $coroutine->desc ($newdesc) |
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348 | |
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349 | Sets (or gets in case the argument is missing) the description for this |
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350 | coroutine. This is just a free-form string you can associate with a coroutine. |
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351 | |
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352 | =cut |
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353 | |
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354 | sub desc { |
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355 | my $old = $_[0]{desc}; |
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356 | $_[0]{desc} = $_[1] if @_ > 1; |
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357 | $old; |
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358 | } |
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359 | |
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360 | =back |
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361 | |
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362 | =head2 GLOBAL FUNCTIONS |
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363 | |
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364 | =over 4 |
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365 | |
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366 | =item Coro::nready |
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367 | |
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368 | Returns the number of coroutines that are currently in the ready state, |
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369 | i.e. that can be swicthed to. The value C<0> means that the only runnable |
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370 | coroutine is the currently running one, so C<cede> would have no effect, |
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371 | and C<schedule> would cause a deadlock unless there is an idle handler |
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372 | that wakes up some coroutines. |
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373 | |
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374 | =item unblock_sub { ... } |
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375 | |
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376 | This utility function takes a BLOCK or code reference and "unblocks" it, |
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377 | returning the new coderef. This means that the new coderef will return |
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378 | immediately without blocking, returning nothing, while the original code |
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379 | ref will be called (with parameters) from within its own coroutine. |
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380 | |
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381 | The reason this fucntion exists is that many event libraries (such as the |
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382 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
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383 | of thread-safety). This means you must not block within event callbacks, |
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384 | otherwise you might suffer from crashes or worse. |
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385 | |
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386 | This function allows your callbacks to block by executing them in another |
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387 | coroutine where it is safe to block. One example where blocking is handy |
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388 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
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389 | disk. |
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390 | |
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391 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
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392 | creating event callbacks that want to block. |
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393 | |
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394 | =cut |
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395 | |
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396 | our @unblock_pool; |
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397 | our @unblock_queue; |
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398 | our $UNBLOCK_POOL_SIZE = 2; |
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399 | |
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400 | sub unblock_handler_ { |
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401 | while () { |
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402 | my ($cb, @arg) = @{ delete $Coro::current->{arg} }; |
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403 | $cb->(@arg); |
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404 | |
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405 | last if @unblock_pool >= $UNBLOCK_POOL_SIZE; |
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406 | push @unblock_pool, $Coro::current; |
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407 | schedule; |
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408 | } |
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409 | } |
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410 | |
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411 | our $unblock_scheduler = async { |
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412 | while () { |
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413 | while (my $cb = pop @unblock_queue) { |
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414 | my $handler = (pop @unblock_pool or new Coro \&unblock_handler_); |
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415 | $handler->{arg} = $cb; |
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416 | $handler->ready; |
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417 | cede; |
70 | } |
418 | } |
71 | } while (1); |
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72 | }, $class; |
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73 | } |
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74 | |
419 | |
75 | =item $prev->transfer($next) |
420 | schedule; |
76 | |
421 | } |
77 | Save the state of the current subroutine in $prev and switch to the |
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78 | coroutine saved in $next. |
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79 | |
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80 | =cut |
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81 | |
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82 | # I call the _transfer function from a perl function |
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83 | # because that way perl saves all important things on |
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84 | # the stack. |
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85 | sub transfer { |
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86 | _transfer($_[0], $_[1]); |
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87 | } |
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88 | |
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89 | =item $error, $error_msg, $error_coro |
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90 | |
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91 | This coroutine will be called on fatal errors. C<$error_msg> and |
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92 | C<$error_coro> return the error message and the error-causing coroutine |
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93 | (NOT an object) respectively. This API might change. |
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94 | |
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95 | =cut |
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96 | |
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97 | $error_msg = |
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98 | $error_coro = undef; |
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99 | |
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100 | $error = _newprocess { |
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101 | print STDERR "FATAL: $error_msg\nprogram aborted\n"; |
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102 | exit 50; |
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103 | }; |
422 | }; |
104 | |
423 | |
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424 | sub unblock_sub(&) { |
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425 | my $cb = shift; |
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426 | |
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427 | sub { |
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428 | push @unblock_queue, [$cb, @_]; |
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429 | $unblock_scheduler->ready; |
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430 | } |
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431 | } |
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432 | |
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433 | =back |
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434 | |
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435 | =cut |
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436 | |
105 | 1; |
437 | 1; |
106 | |
438 | |
107 | =back |
439 | =head1 BUGS/LIMITATIONS |
108 | |
440 | |
109 | =head1 BUGS |
441 | - you must make very sure that no coro is still active on global |
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442 | destruction. very bad things might happen otherwise (usually segfaults). |
110 | |
443 | |
111 | This module has not yet been extensively tested. |
444 | - this module is not thread-safe. You should only ever use this module |
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445 | from the same thread (this requirement might be losened in the future |
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446 | to allow per-thread schedulers, but Coro::State does not yet allow |
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447 | this). |
112 | |
448 | |
113 | =head1 SEE ALSO |
449 | =head1 SEE ALSO |
114 | |
450 | |
115 | L<Coro::Process>, L<Coro::Signal>. |
451 | Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
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452 | |
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453 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
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454 | |
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455 | Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
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456 | |
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457 | Embedding: L<Coro:MakeMaker> |
116 | |
458 | |
117 | =head1 AUTHOR |
459 | =head1 AUTHOR |
118 | |
460 | |
119 | Marc Lehmann <pcg@goof.com> |
461 | Marc Lehmann <schmorp@schmorp.de> |
120 | http://www.goof.com/pcg/marc/ |
462 | http://home.schmorp.de/ |
121 | |
463 | |
122 | =cut |
464 | =cut |
123 | |
465 | |