1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - coroutine process abstraction |
3 | Coro - the only real threads in perl |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro; |
7 | use Coro; |
8 | |
8 | |
… | |
… | |
11 | print "2\n"; |
11 | print "2\n"; |
12 | cede; # yield back to main |
12 | cede; # yield back to main |
13 | print "4\n"; |
13 | print "4\n"; |
14 | }; |
14 | }; |
15 | print "1\n"; |
15 | print "1\n"; |
16 | cede; # yield to coroutine |
16 | cede; # yield to coro |
17 | print "3\n"; |
17 | print "3\n"; |
18 | cede; # and again |
18 | cede; # and again |
19 | |
19 | |
20 | # use locking |
20 | # use locking |
21 | use Coro::Semaphore; |
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22 | my $lock = new Coro::Semaphore; |
21 | my $lock = new Coro::Semaphore; |
23 | my $locked; |
22 | my $locked; |
24 | |
23 | |
25 | $lock->down; |
24 | $lock->down; |
26 | $locked = 1; |
25 | $locked = 1; |
27 | $lock->up; |
26 | $lock->up; |
28 | |
27 | |
29 | =head1 DESCRIPTION |
28 | =head1 DESCRIPTION |
30 | |
29 | |
31 | This module collection manages coroutines. Coroutines are similar to |
30 | For a tutorial-style introduction, please read the L<Coro::Intro> |
32 | threads but don't (in general) run in parallel at the same time even |
31 | manpage. This manpage mainly contains reference information. |
33 | on SMP machines. The specific flavor of coroutine used in this module |
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34 | also guarantees you that it will not switch between coroutines unless |
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35 | necessary, at easily-identified points in your program, so locking and |
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36 | parallel access are rarely an issue, making coroutine programming much |
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37 | safer and easier than threads programming. |
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38 | |
32 | |
39 | Unlike a normal perl program, however, coroutines allow you to have |
33 | This module collection manages continuations in general, most often in |
40 | multiple running interpreters that share data, which is especially useful |
34 | the form of cooperative threads (also called coros, or simply "coro" |
41 | to code pseudo-parallel processes and for event-based programming, such as |
35 | in the documentation). They are similar to kernel threads but don't (in |
42 | multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to |
36 | general) run in parallel at the same time even on SMP machines. The |
43 | learn more. |
37 | specific flavor of thread offered by this module also guarantees you that |
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38 | it will not switch between threads unless necessary, at easily-identified |
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39 | points in your program, so locking and parallel access are rarely an |
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40 | issue, making thread programming much safer and easier than using other |
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41 | thread models. |
44 | |
42 | |
45 | Coroutines are also useful because Perl has no support for threads (the so |
43 | Unlike the so-called "Perl threads" (which are not actually real threads |
46 | called "threads" that perl offers are nothing more than the (bad) process |
44 | but only the windows process emulation (see section of same name for |
47 | emulation coming from the Windows platform: On standard operating systems |
45 | more details) ported to UNIX, and as such act as processes), Coro |
48 | they serve no purpose whatsoever, except by making your programs slow and |
46 | provides a full shared address space, which makes communication between |
49 | making them use a lot of memory. Best disable them when building perl, or |
47 | threads very easy. And coro threads are fast, too: disabling the Windows |
50 | aks your software vendor/distributor to do it for you). |
48 | process emulation code in your perl and using Coro can easily result in |
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49 | a two to four times speed increase for your programs. A parallel matrix |
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50 | multiplication benchmark (very communication-intensive) runs over 300 |
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51 | times faster on a single core than perls pseudo-threads on a quad core |
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52 | using all four cores. |
51 | |
53 | |
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54 | Coro achieves that by supporting multiple running interpreters that share |
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55 | data, which is especially useful to code pseudo-parallel processes and |
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56 | for event-based programming, such as multiple HTTP-GET requests running |
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57 | concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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58 | into an event-based environment. |
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59 | |
52 | In this module, coroutines are defined as "callchain + lexical variables + |
60 | In this module, a thread is defined as "callchain + lexical variables + |
53 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
61 | some package variables + C stack), that is, a thread has its own callchain, |
54 | its own set of lexicals and its own set of perls most important global |
62 | its own set of lexicals and its own set of perls most important global |
55 | variables (see L<Coro::State> for more configuration). |
63 | variables (see L<Coro::State> for more configuration and background info). |
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64 | |
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65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
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66 | module family is quite large. |
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67 | |
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68 | =head1 CORO THREAD LIFE CYCLE |
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69 | |
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70 | During the long and exciting (or not) life of a coro thread, it goes |
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71 | through a number of states: |
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72 | |
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73 | =over 4 |
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74 | |
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75 | =item 1. Creation |
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76 | |
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77 | The first thing in the life of a coro thread is it's creation - |
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78 | obviously. The typical way to create a thread is to call the C<async |
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79 | BLOCK> function: |
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80 | |
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81 | async { |
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82 | # thread code goes here |
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83 | }; |
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84 | |
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85 | You can also pass arguments, which are put in C<@_>: |
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86 | |
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87 | async { |
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88 | print $_[1]; # prints 2 |
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89 | } 1, 2, 3; |
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90 | |
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91 | This creates a new coro thread and puts it into the ready queue, meaning |
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92 | it will run as soon as the CPU is free for it. |
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93 | |
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94 | C<async> will return a Coro object - you can store this for future |
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95 | reference or ignore it - a thread that is running, ready to run or waiting |
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96 | for some event is alive on it's own. |
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97 | |
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98 | Another way to create a thread is to call the C<new> constructor with a |
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99 | code-reference: |
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100 | |
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101 | new Coro sub { |
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102 | # thread code goes here |
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103 | }, @optional_arguments; |
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104 | |
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105 | This is quite similar to calling C<async>, but the important difference is |
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106 | that the new thread is not put into the ready queue, so the thread will |
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107 | not run until somebody puts it there. C<async> is, therefore, identical to |
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108 | this sequence: |
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109 | |
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110 | my $coro = new Coro sub { |
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111 | # thread code goes here |
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112 | }; |
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113 | $coro->ready; |
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114 | return $coro; |
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115 | |
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116 | =item 2. Startup |
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117 | |
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118 | When a new coro thread is created, only a copy of the code reference |
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119 | and the arguments are stored, no extra memory for stacks and so on is |
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120 | allocated, keeping the coro thread in a low-memory state. |
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121 | |
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122 | Only when it actually starts executing will all the resources be finally |
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123 | allocated. |
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124 | |
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125 | The optional arguments specified at coro creation are available in C<@_>, |
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126 | similar to function calls. |
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127 | |
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128 | =item 3. Running / Blocking |
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129 | |
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130 | A lot can happen after the coro thread has started running. Quite usually, |
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131 | it will not run to the end in one go (because you could use a function |
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132 | instead), but it will give up the CPU regularly because it waits for |
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133 | external events. |
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134 | |
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135 | As long as a coro thread runs, its Coro object is available in the global |
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136 | variable C<$Coro::current>. |
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137 | |
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138 | The low-level way to give up the CPU is to call the scheduler, which |
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139 | selects a new coro thread to run: |
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140 | |
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141 | Coro::schedule; |
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142 | |
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143 | Since running threads are not in the ready queue, calling the scheduler |
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144 | without doing anything else will block the coro thread forever - you need |
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145 | to arrange either for the coro to put woken up (readied) by some other |
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146 | event or some other thread, or you can put it into the ready queue before |
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147 | scheduling: |
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148 | |
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149 | # this is exactly what Coro::cede does |
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150 | $Coro::current->ready; |
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151 | Coro::schedule; |
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152 | |
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153 | All the higher-level synchronisation methods (Coro::Semaphore, |
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154 | Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<< |
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155 | Coro::schedule >>. |
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156 | |
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157 | While the coro thread is running it also might get assigned a C-level |
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158 | thread, or the C-level thread might be unassigned from it, as the Coro |
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159 | runtime wishes. A C-level thread needs to be assigned when your perl |
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160 | thread calls into some C-level function and that function in turn calls |
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161 | perl and perl then wants to switch coroutines. This happens most often |
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162 | when you run an event loop and block in the callback, or when perl |
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163 | itself calls some function such as C<AUTOLOAD> or methods via the C<tie> |
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164 | mechanism. |
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165 | |
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166 | =item 4. Termination |
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167 | |
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168 | Many threads actually terminate after some time. There are a number of |
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169 | ways to terminate a coro thread, the simplest is returning from the |
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170 | top-level code reference: |
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171 | |
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172 | async { |
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173 | # after returning from here, the coro thread is terminated |
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174 | }; |
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175 | |
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176 | async { |
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177 | return if 0.5 < rand; # terminate a little earlier, maybe |
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178 | print "got a chance to print this\n"; |
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179 | # or here |
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180 | }; |
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181 | |
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182 | Any values returned from the coroutine can be recovered using C<< ->join |
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183 | >>: |
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184 | |
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185 | my $coro = async { |
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186 | "hello, world\n" # return a string |
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187 | }; |
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188 | |
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189 | my $hello_world = $coro->join; |
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190 | |
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191 | print $hello_world; |
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192 | |
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193 | Another way to terminate is to call C<< Coro::terminate >>, which at any |
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194 | subroutine call nesting level: |
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195 | |
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196 | async { |
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197 | Coro::terminate "return value 1", "return value 2"; |
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198 | }; |
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199 | |
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200 | And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the |
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201 | coro thread from another thread: |
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202 | |
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203 | my $coro = async { |
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204 | exit 1; |
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205 | }; |
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206 | |
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207 | $coro->cancel; # also accepts values for ->join to retrieve |
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208 | |
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209 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
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210 | actually exiting, and might leave C libraries and XS modules in a weird |
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211 | state. Unlike other thread implementations, however, Coro is exceptionally |
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212 | safe with regards to cancellation, as perl will always be in a consistent |
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213 | state, and for those cases where you want to do truly marvellous things |
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214 | with your coro while it is being cancelled - that is, make sure all |
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215 | cleanup code is executed from the thread being cancelled - there is even a |
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216 | C<< ->safe_cancel >> method. |
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217 | |
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218 | So, cancelling a thread that runs in an XS event loop might not be the |
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219 | best idea, but any other combination that deals with perl only (cancelling |
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220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
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221 | safe. |
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222 | |
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223 | Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
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224 | automatically - just like other objects in Perl. This is not such a common |
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225 | case, however - a running thread is referencedy b C<$Coro::current>, a |
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226 | thread ready to run is referenced by the ready queue, a thread waiting |
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227 | on a lock or semaphore is referenced by being in some wait list and so |
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228 | on. But a thread that isn't in any of those queues gets cancelled: |
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229 | |
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230 | async { |
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231 | schedule; # cede to other coros, don't go into the ready queue |
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232 | }; |
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233 | |
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234 | cede; |
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235 | # now the async above is destroyed, as it is not referenced by anything. |
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236 | |
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237 | =item 5. Cleanup |
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238 | |
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239 | Threads will allocate various resources. Most but not all will be returned |
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240 | when a thread terminates, during clean-up. |
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241 | |
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242 | Cleanup is quite similar to throwing an uncaught exception: perl will |
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243 | work it's way up through all subroutine calls and blocks. On it's way, it |
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244 | will release all C<my> variables, undo all C<local>'s and free any other |
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245 | resources truly local to the thread. |
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246 | |
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247 | So, a common way to free resources is to keep them referenced only by my |
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248 | variables: |
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249 | |
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250 | async { |
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251 | my $big_cache = new Cache ...; |
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252 | }; |
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253 | |
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254 | If there are no other references, then the C<$big_cache> object will be |
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255 | freed when the thread terminates, regardless of how it does so. |
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256 | |
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257 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
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258 | resources, but that's where the C<guard> methods come in handy: |
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259 | |
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260 | my $sem = new Coro::Semaphore; |
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261 | |
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262 | async { |
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263 | my $lock_guard = $sem->guard; |
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264 | # if we reutrn, or die or get cancelled, here, |
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265 | # then the semaphore will be "up"ed. |
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266 | }; |
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267 | |
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268 | The C<Guard::guard> function comes in handy for any custom cleanup you |
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269 | might want to do (but you cannot switch to other coroutines form those |
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270 | code blocks): |
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271 | |
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272 | async { |
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273 | my $window = new Gtk2::Window "toplevel"; |
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274 | # The window will not be cleaned up automatically, even when $window |
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275 | # gets freed, so use a guard to ensure it's destruction |
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276 | # in case of an error: |
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277 | my $window_guard = Guard::guard { $window->destroy }; |
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278 | |
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279 | # we are safe here |
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280 | }; |
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281 | |
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282 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
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283 | replacing the coro thread description: |
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284 | |
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285 | sub myfunction { |
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286 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
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287 | |
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288 | # if we return or die here, the description will be restored |
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289 | } |
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290 | |
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291 | =item 6. Viva La Zombie Muerte |
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292 | |
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293 | Even after a thread has terminated and cleaned up its resources, the Coro |
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294 | object still is there and stores the return values of the thread. |
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295 | |
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296 | The means the Coro object gets freed automatically when the thread has |
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297 | terminated and cleaned up and there arenot other references. |
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298 | |
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299 | If there are, the Coro object will stay around, and you can call C<< |
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300 | ->join >> as many times as you wish to retrieve the result values: |
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301 | |
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302 | async { |
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303 | print "hi\n"; |
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304 | 1 |
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305 | }; |
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306 | |
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307 | # run the async above, and free everything before returning |
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308 | # from Coro::cede: |
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309 | Coro::cede; |
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310 | |
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311 | { |
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312 | my $coro = async { |
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313 | print "hi\n"; |
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314 | 1 |
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315 | }; |
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316 | |
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317 | # run the async above, and clean up, but do not free the coro |
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318 | # object: |
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319 | Coro::cede; |
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320 | |
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321 | # optionally retrieve the result values |
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322 | my @results = $coro->join; |
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323 | |
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324 | # now $coro goes out of scope, and presumably gets freed |
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325 | }; |
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326 | |
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327 | =back |
56 | |
328 | |
57 | =cut |
329 | =cut |
58 | |
330 | |
59 | package Coro; |
331 | package Coro; |
60 | |
332 | |
61 | use strict qw(vars subs); |
333 | use common::sense; |
62 | no warnings "uninitialized"; |
334 | |
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335 | use Carp (); |
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336 | |
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337 | use Guard (); |
63 | |
338 | |
64 | use Coro::State; |
339 | use Coro::State; |
65 | |
340 | |
66 | use base qw(Coro::State Exporter); |
341 | use base qw(Coro::State Exporter); |
67 | |
342 | |
68 | our $idle; # idle handler |
343 | our $idle; # idle handler |
69 | our $main; # main coroutine |
344 | our $main; # main coro |
70 | our $current; # current coroutine |
345 | our $current; # current coro |
71 | |
346 | |
72 | our $VERSION = "5.0"; |
347 | our $VERSION = 5.372; |
73 | |
348 | |
74 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
349 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
75 | our %EXPORT_TAGS = ( |
350 | our %EXPORT_TAGS = ( |
76 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
351 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
77 | ); |
352 | ); |
78 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
353 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
79 | |
354 | |
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355 | =head1 GLOBAL VARIABLES |
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356 | |
80 | =over 4 |
357 | =over 4 |
81 | |
358 | |
82 | =item $Coro::main |
359 | =item $Coro::main |
83 | |
360 | |
84 | This variable stores the coroutine object that represents the main |
361 | This variable stores the Coro object that represents the main |
85 | program. While you cna C<ready> it and do most other things you can do to |
362 | program. While you cna C<ready> it and do most other things you can do to |
86 | coroutines, it is mainly useful to compare again C<$Coro::current>, to see |
363 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
87 | whether you are running in the main program or not. |
364 | whether you are running in the main program or not. |
88 | |
365 | |
89 | =cut |
366 | =cut |
90 | |
367 | |
91 | # $main is now being initialised by Coro::State |
368 | # $main is now being initialised by Coro::State |
92 | |
369 | |
93 | =item $Coro::current |
370 | =item $Coro::current |
94 | |
371 | |
95 | The coroutine object representing the current coroutine (the last |
372 | The Coro object representing the current coro (the last |
96 | coroutine that the Coro scheduler switched to). The initial value is |
373 | coro that the Coro scheduler switched to). The initial value is |
97 | C<$Coro::main> (of course). |
374 | C<$Coro::main> (of course). |
98 | |
375 | |
99 | This variable is B<strictly> I<read-only>. You can take copies of the |
376 | This variable is B<strictly> I<read-only>. You can take copies of the |
100 | value stored in it and use it as any other coroutine object, but you must |
377 | value stored in it and use it as any other Coro object, but you must |
101 | not otherwise modify the variable itself. |
378 | not otherwise modify the variable itself. |
102 | |
379 | |
103 | =cut |
380 | =cut |
104 | |
381 | |
105 | sub current() { $current } # [DEPRECATED] |
382 | sub current() { $current } # [DEPRECATED] |
106 | |
383 | |
107 | =item $Coro::idle |
384 | =item $Coro::idle |
108 | |
385 | |
109 | This variable is mainly useful to integrate Coro into event loops. It is |
386 | This variable is mainly useful to integrate Coro into event loops. It is |
110 | usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is |
387 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
111 | pretty low-level functionality. |
388 | pretty low-level functionality. |
112 | |
389 | |
113 | This variable stores a callback that is called whenever the scheduler |
390 | This variable stores a Coro object that is put into the ready queue when |
114 | finds no ready coroutines to run. The default implementation prints |
391 | there are no other ready threads (without invoking any ready hooks). |
115 | "FATAL: deadlock detected" and exits, because the program has no other way |
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116 | to continue. |
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117 | |
392 | |
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393 | The default implementation dies with "FATAL: deadlock detected.", followed |
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394 | by a thread listing, because the program has no other way to continue. |
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395 | |
118 | This hook is overwritten by modules such as C<Coro::Timer> and |
396 | This hook is overwritten by modules such as C<Coro::EV> and |
119 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
397 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
120 | coroutine so the scheduler can run it. |
398 | coro so the scheduler can run it. |
121 | |
399 | |
122 | Note that the callback I<must not>, under any circumstances, block |
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123 | the current coroutine. Normally, this is achieved by having an "idle |
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124 | coroutine" that calls the event loop and then blocks again, and then |
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125 | readying that coroutine in the idle handler. |
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126 | |
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127 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
400 | See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
128 | technique. |
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129 | |
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130 | Please note that if your callback recursively invokes perl (e.g. for event |
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131 | handlers), then it must be prepared to be called recursively itself. |
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132 | |
401 | |
133 | =cut |
402 | =cut |
134 | |
403 | |
135 | $idle = sub { |
404 | # ||= because other modules could have provided their own by now |
136 | require Carp; |
405 | $idle ||= new Coro sub { |
137 | Carp::croak ("FATAL: deadlock detected"); |
406 | require Coro::Debug; |
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407 | die "FATAL: deadlock detected.\n" |
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408 | . Coro::Debug::ps_listing (); |
138 | }; |
409 | }; |
139 | |
410 | |
140 | # this coroutine is necessary because a coroutine |
411 | # this coro is necessary because a coro |
141 | # cannot destroy itself. |
412 | # cannot destroy itself. |
142 | our @destroy; |
413 | our @destroy; |
143 | our $manager; |
414 | our $manager; |
144 | |
415 | |
145 | $manager = new Coro sub { |
416 | $manager = new Coro sub { |
146 | while () { |
417 | while () { |
147 | Coro::_cancel shift @destroy |
418 | _destroy shift @destroy |
148 | while @destroy; |
419 | while @destroy; |
149 | |
420 | |
150 | &schedule; |
421 | &schedule; |
151 | } |
422 | } |
152 | }; |
423 | }; |
153 | $manager->{desc} = "[coro manager]"; |
424 | $manager->{desc} = "[coro manager]"; |
154 | $manager->prio (PRIO_MAX); |
425 | $manager->prio (PRIO_MAX); |
155 | |
426 | |
156 | =back |
427 | =back |
157 | |
428 | |
158 | =head2 SIMPLE COROUTINE CREATION |
429 | =head1 SIMPLE CORO CREATION |
159 | |
430 | |
160 | =over 4 |
431 | =over 4 |
161 | |
432 | |
162 | =item async { ... } [@args...] |
433 | =item async { ... } [@args...] |
163 | |
434 | |
164 | Create a new coroutine and return it's coroutine object (usually |
435 | Create a new coro and return its Coro object (usually |
165 | unused). The coroutine will be put into the ready queue, so |
436 | unused). The coro will be put into the ready queue, so |
166 | it will start running automatically on the next scheduler run. |
437 | it will start running automatically on the next scheduler run. |
167 | |
438 | |
168 | The first argument is a codeblock/closure that should be executed in the |
439 | The first argument is a codeblock/closure that should be executed in the |
169 | coroutine. When it returns argument returns the coroutine is automatically |
440 | coro. When it returns argument returns the coro is automatically |
170 | terminated. |
441 | terminated. |
171 | |
442 | |
172 | The remaining arguments are passed as arguments to the closure. |
443 | The remaining arguments are passed as arguments to the closure. |
173 | |
444 | |
174 | See the C<Coro::State::new> constructor for info about the coroutine |
445 | See the C<Coro::State::new> constructor for info about the coro |
175 | environment in which coroutines are executed. |
446 | environment in which coro are executed. |
176 | |
447 | |
177 | Calling C<exit> in a coroutine will do the same as calling exit outside |
448 | Calling C<exit> in a coro will do the same as calling exit outside |
178 | the coroutine. Likewise, when the coroutine dies, the program will exit, |
449 | the coro. Likewise, when the coro dies, the program will exit, |
179 | just as it would in the main program. |
450 | just as it would in the main program. |
180 | |
451 | |
181 | If you do not want that, you can provide a default C<die> handler, or |
452 | If you do not want that, you can provide a default C<die> handler, or |
182 | simply avoid dieing (by use of C<eval>). |
453 | simply avoid dieing (by use of C<eval>). |
183 | |
454 | |
184 | Example: Create a new coroutine that just prints its arguments. |
455 | Example: Create a new coro that just prints its arguments. |
185 | |
456 | |
186 | async { |
457 | async { |
187 | print "@_\n"; |
458 | print "@_\n"; |
188 | } 1,2,3,4; |
459 | } 1,2,3,4; |
189 | |
460 | |
190 | =cut |
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191 | |
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192 | sub async(&@) { |
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193 | my $coro = new Coro @_; |
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194 | $coro->ready; |
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195 | $coro |
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196 | } |
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197 | |
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198 | =item async_pool { ... } [@args...] |
461 | =item async_pool { ... } [@args...] |
199 | |
462 | |
200 | Similar to C<async>, but uses a coroutine pool, so you should not call |
463 | Similar to C<async>, but uses a coro pool, so you should not call |
201 | terminate or join on it (although you are allowed to), and you get a |
464 | terminate or join on it (although you are allowed to), and you get a |
202 | coroutine that might have executed other code already (which can be good |
465 | coro that might have executed other code already (which can be good |
203 | or bad :). |
466 | or bad :). |
204 | |
467 | |
205 | On the plus side, this function is about twice as fast as creating (and |
468 | On the plus side, this function is about twice as fast as creating (and |
206 | destroying) a completely new coroutine, so if you need a lot of generic |
469 | destroying) a completely new coro, so if you need a lot of generic |
207 | coroutines in quick successsion, use C<async_pool>, not C<async>. |
470 | coros in quick successsion, use C<async_pool>, not C<async>. |
208 | |
471 | |
209 | The code block is executed in an C<eval> context and a warning will be |
472 | The code block is executed in an C<eval> context and a warning will be |
210 | issued in case of an exception instead of terminating the program, as |
473 | issued in case of an exception instead of terminating the program, as |
211 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
474 | C<async> does. As the coro is being reused, stuff like C<on_destroy> |
212 | will not work in the expected way, unless you call terminate or cancel, |
475 | will not work in the expected way, unless you call terminate or cancel, |
213 | which somehow defeats the purpose of pooling (but is fine in the |
476 | which somehow defeats the purpose of pooling (but is fine in the |
214 | exceptional case). |
477 | exceptional case). |
215 | |
478 | |
216 | The priority will be reset to C<0> after each run, tracing will be |
479 | The priority will be reset to C<0> after each run, tracing will be |
217 | disabled, the description will be reset and the default output filehandle |
480 | disabled, the description will be reset and the default output filehandle |
218 | gets restored, so you can change all these. Otherwise the coroutine will |
481 | gets restored, so you can change all these. Otherwise the coro will |
219 | be re-used "as-is": most notably if you change other per-coroutine global |
482 | be re-used "as-is": most notably if you change other per-coro global |
220 | stuff such as C<$/> you I<must needs> revert that change, which is most |
483 | stuff such as C<$/> you I<must needs> revert that change, which is most |
221 | simply done by using local as in: C<< local $/ >>. |
484 | simply done by using local as in: C<< local $/ >>. |
222 | |
485 | |
223 | The idle pool size is limited to C<8> idle coroutines (this can be |
486 | The idle pool size is limited to C<8> idle coros (this can be |
224 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
487 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
225 | coros as required. |
488 | coros as required. |
226 | |
489 | |
227 | If you are concerned about pooled coroutines growing a lot because a |
490 | If you are concerned about pooled coros growing a lot because a |
228 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
491 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
229 | { terminate }> once per second or so to slowly replenish the pool. In |
492 | { terminate }> once per second or so to slowly replenish the pool. In |
230 | addition to that, when the stacks used by a handler grows larger than 16kb |
493 | addition to that, when the stacks used by a handler grows larger than 32kb |
231 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
494 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
232 | |
495 | |
233 | =cut |
496 | =cut |
234 | |
497 | |
235 | our $POOL_SIZE = 8; |
498 | our $POOL_SIZE = 8; |
236 | our $POOL_RSS = 16 * 1024; |
499 | our $POOL_RSS = 32 * 1024; |
237 | our @async_pool; |
500 | our @async_pool; |
238 | |
501 | |
239 | sub pool_handler { |
502 | sub pool_handler { |
240 | while () { |
503 | while () { |
241 | eval { |
504 | eval { |
… | |
… | |
246 | } |
509 | } |
247 | } |
510 | } |
248 | |
511 | |
249 | =back |
512 | =back |
250 | |
513 | |
251 | =head2 STATIC METHODS |
514 | =head1 STATIC METHODS |
252 | |
515 | |
253 | Static methods are actually functions that operate on the current coroutine. |
516 | Static methods are actually functions that implicitly operate on the |
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517 | current coro. |
254 | |
518 | |
255 | =over 4 |
519 | =over 4 |
256 | |
520 | |
257 | =item schedule |
521 | =item schedule |
258 | |
522 | |
259 | Calls the scheduler. The scheduler will find the next coroutine that is |
523 | Calls the scheduler. The scheduler will find the next coro that is |
260 | to be run from the ready queue and switches to it. The next coroutine |
524 | to be run from the ready queue and switches to it. The next coro |
261 | to be run is simply the one with the highest priority that is longest |
525 | to be run is simply the one with the highest priority that is longest |
262 | in its ready queue. If there is no coroutine ready, it will clal the |
526 | in its ready queue. If there is no coro ready, it will call the |
263 | C<$Coro::idle> hook. |
527 | C<$Coro::idle> hook. |
264 | |
528 | |
265 | Please note that the current coroutine will I<not> be put into the ready |
529 | Please note that the current coro will I<not> be put into the ready |
266 | queue, so calling this function usually means you will never be called |
530 | queue, so calling this function usually means you will never be called |
267 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
531 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
268 | thus waking you up. |
532 | thus waking you up. |
269 | |
533 | |
270 | This makes C<schedule> I<the> generic method to use to block the current |
534 | This makes C<schedule> I<the> generic method to use to block the current |
271 | coroutine and wait for events: first you remember the current coroutine in |
535 | coro and wait for events: first you remember the current coro in |
272 | a variable, then arrange for some callback of yours to call C<< ->ready |
536 | a variable, then arrange for some callback of yours to call C<< ->ready |
273 | >> on that once some event happens, and last you call C<schedule> to put |
537 | >> on that once some event happens, and last you call C<schedule> to put |
274 | yourself to sleep. Note that a lot of things can wake your coroutine up, |
538 | yourself to sleep. Note that a lot of things can wake your coro up, |
275 | so you need to check whether the event indeed happened, e.g. by storing the |
539 | so you need to check whether the event indeed happened, e.g. by storing the |
276 | status in a variable. |
540 | status in a variable. |
277 | |
541 | |
278 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
542 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
279 | |
543 | |
280 | =item cede |
544 | =item cede |
281 | |
545 | |
282 | "Cede" to other coroutines. This function puts the current coroutine into |
546 | "Cede" to other coros. This function puts the current coro into |
283 | the ready queue and calls C<schedule>, which has the effect of giving |
547 | the ready queue and calls C<schedule>, which has the effect of giving |
284 | up the current "timeslice" to other coroutines of the same or higher |
548 | up the current "timeslice" to other coros of the same or higher |
285 | priority. Once your coroutine gets its turn again it will automatically be |
549 | priority. Once your coro gets its turn again it will automatically be |
286 | resumed. |
550 | resumed. |
287 | |
551 | |
288 | This function is often called C<yield> in other languages. |
552 | This function is often called C<yield> in other languages. |
289 | |
553 | |
290 | =item Coro::cede_notself |
554 | =item Coro::cede_notself |
291 | |
555 | |
292 | Works like cede, but is not exported by default and will cede to I<any> |
556 | Works like cede, but is not exported by default and will cede to I<any> |
293 | coroutine, regardless of priority. This is useful sometimes to ensure |
557 | coro, regardless of priority. This is useful sometimes to ensure |
294 | progress is made. |
558 | progress is made. |
295 | |
559 | |
296 | =item terminate [arg...] |
560 | =item terminate [arg...] |
297 | |
561 | |
298 | Terminates the current coroutine with the given status values (see L<cancel>). |
562 | Terminates the current coro with the given status values (see |
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563 | L<cancel>). The values will not be copied, but referenced directly. |
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|
564 | |
|
|
565 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
|
|
566 | |
|
|
567 | These function install enter and leave winders in the current scope. The |
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568 | enter block will be executed when on_enter is called and whenever the |
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569 | current coro is re-entered by the scheduler, while the leave block is |
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570 | executed whenever the current coro is blocked by the scheduler, and |
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571 | also when the containing scope is exited (by whatever means, be it exit, |
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|
572 | die, last etc.). |
|
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573 | |
|
|
574 | I<Neither invoking the scheduler, nor exceptions, are allowed within those |
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575 | BLOCKs>. That means: do not even think about calling C<die> without an |
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576 | eval, and do not even think of entering the scheduler in any way. |
|
|
577 | |
|
|
578 | Since both BLOCKs are tied to the current scope, they will automatically |
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579 | be removed when the current scope exits. |
|
|
580 | |
|
|
581 | These functions implement the same concept as C<dynamic-wind> in scheme |
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|
582 | does, and are useful when you want to localise some resource to a specific |
|
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583 | coro. |
|
|
584 | |
|
|
585 | They slow down thread switching considerably for coros that use them |
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586 | (about 40% for a BLOCK with a single assignment, so thread switching is |
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587 | still reasonably fast if the handlers are fast). |
|
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588 | |
|
|
589 | These functions are best understood by an example: The following function |
|
|
590 | will change the current timezone to "Antarctica/South_Pole", which |
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591 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
|
|
592 | which remember/change the current timezone and restore the previous |
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593 | value, respectively, the timezone is only changed for the coro that |
|
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594 | installed those handlers. |
|
|
595 | |
|
|
596 | use POSIX qw(tzset); |
|
|
597 | |
|
|
598 | async { |
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599 | my $old_tz; # store outside TZ value here |
|
|
600 | |
|
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601 | Coro::on_enter { |
|
|
602 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
603 | |
|
|
604 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
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605 | tzset; # enable new value |
|
|
606 | }; |
|
|
607 | |
|
|
608 | Coro::on_leave { |
|
|
609 | $ENV{TZ} = $old_tz; |
|
|
610 | tzset; # restore old value |
|
|
611 | }; |
|
|
612 | |
|
|
613 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
614 | # without disturbing the TZ of any other coro. |
|
|
615 | }; |
|
|
616 | |
|
|
617 | This can be used to localise about any resource (locale, uid, current |
|
|
618 | working directory etc.) to a block, despite the existance of other |
|
|
619 | coros. |
|
|
620 | |
|
|
621 | Another interesting example implements time-sliced multitasking using |
|
|
622 | interval timers (this could obviously be optimised, but does the job): |
|
|
623 | |
|
|
624 | # "timeslice" the given block |
|
|
625 | sub timeslice(&) { |
|
|
626 | use Time::HiRes (); |
|
|
627 | |
|
|
628 | Coro::on_enter { |
|
|
629 | # on entering the thread, we set an VTALRM handler to cede |
|
|
630 | $SIG{VTALRM} = sub { cede }; |
|
|
631 | # and then start the interval timer |
|
|
632 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
633 | }; |
|
|
634 | Coro::on_leave { |
|
|
635 | # on leaving the thread, we stop the interval timer again |
|
|
636 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
637 | }; |
|
|
638 | |
|
|
639 | &{+shift}; |
|
|
640 | } |
|
|
641 | |
|
|
642 | # use like this: |
|
|
643 | timeslice { |
|
|
644 | # The following is an endless loop that would normally |
|
|
645 | # monopolise the process. Since it runs in a timesliced |
|
|
646 | # environment, it will regularly cede to other threads. |
|
|
647 | while () { } |
|
|
648 | }; |
|
|
649 | |
299 | |
650 | |
300 | =item killall |
651 | =item killall |
301 | |
652 | |
302 | Kills/terminates/cancels all coroutines except the currently running |
653 | Kills/terminates/cancels all coros except the currently running one. |
303 | one. This is useful after a fork, either in the child or the parent, as |
|
|
304 | usually only one of them should inherit the running coroutines. |
|
|
305 | |
654 | |
306 | Note that while this will try to free some of the main programs resources, |
655 | Note that while this will try to free some of the main interpreter |
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|
656 | resources if the calling coro isn't the main coro, but one |
307 | you cannot free all of them, so if a coroutine that is not the main |
657 | cannot free all of them, so if a coro that is not the main coro |
308 | program calls this function, there will be some one-time resource leak. |
658 | calls this function, there will be some one-time resource leak. |
309 | |
659 | |
310 | =cut |
660 | =cut |
311 | |
661 | |
312 | sub killall { |
662 | sub killall { |
313 | for (Coro::State::list) { |
663 | for (Coro::State::list) { |
… | |
… | |
316 | } |
666 | } |
317 | } |
667 | } |
318 | |
668 | |
319 | =back |
669 | =back |
320 | |
670 | |
321 | =head2 COROUTINE METHODS |
671 | =head1 CORO OBJECT METHODS |
322 | |
672 | |
323 | These are the methods you can call on coroutine objects (or to create |
673 | These are the methods you can call on coro objects (or to create |
324 | them). |
674 | them). |
325 | |
675 | |
326 | =over 4 |
676 | =over 4 |
327 | |
677 | |
328 | =item new Coro \&sub [, @args...] |
678 | =item new Coro \&sub [, @args...] |
329 | |
679 | |
330 | Create a new coroutine and return it. When the sub returns, the coroutine |
680 | Create a new coro and return it. When the sub returns, the coro |
331 | automatically terminates as if C<terminate> with the returned values were |
681 | automatically terminates as if C<terminate> with the returned values were |
332 | called. To make the coroutine run you must first put it into the ready |
682 | called. To make the coro run you must first put it into the ready |
333 | queue by calling the ready method. |
683 | queue by calling the ready method. |
334 | |
684 | |
335 | See C<async> and C<Coro::State::new> for additional info about the |
685 | See C<async> and C<Coro::State::new> for additional info about the |
336 | coroutine environment. |
686 | coro environment. |
337 | |
687 | |
338 | =cut |
688 | =cut |
339 | |
689 | |
340 | sub _terminate { |
690 | sub _coro_run { |
341 | terminate &{+shift}; |
691 | terminate &{+shift}; |
342 | } |
692 | } |
343 | |
693 | |
344 | =item $success = $coroutine->ready |
694 | =item $success = $coro->ready |
345 | |
695 | |
346 | Put the given coroutine into the end of its ready queue (there is one |
696 | Put the given coro into the end of its ready queue (there is one |
347 | queue for each priority) and return true. If the coroutine is already in |
697 | queue for each priority) and return true. If the coro is already in |
348 | the ready queue, do nothing and return false. |
698 | the ready queue, do nothing and return false. |
349 | |
699 | |
350 | This ensures that the scheduler will resume this coroutine automatically |
700 | This ensures that the scheduler will resume this coro automatically |
351 | once all the coroutines of higher priority and all coroutines of the same |
701 | once all the coro of higher priority and all coro of the same |
352 | priority that were put into the ready queue earlier have been resumed. |
702 | priority that were put into the ready queue earlier have been resumed. |
353 | |
703 | |
|
|
704 | =item $coro->suspend |
|
|
705 | |
|
|
706 | Suspends the specified coro. A suspended coro works just like any other |
|
|
707 | coro, except that the scheduler will not select a suspended coro for |
|
|
708 | execution. |
|
|
709 | |
|
|
710 | Suspending a coro can be useful when you want to keep the coro from |
|
|
711 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
712 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
713 | |
|
|
714 | A scenario for the former would be to suspend all (other) coros after a |
|
|
715 | fork and keep them alive, so their destructors aren't called, but new |
|
|
716 | coros can be created. |
|
|
717 | |
|
|
718 | =item $coro->resume |
|
|
719 | |
|
|
720 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
721 | the coro was in the ready queue when it was suspended, it might have been |
|
|
722 | unreadied by the scheduler, so an activation might have been lost. |
|
|
723 | |
|
|
724 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
725 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
726 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
727 | that. |
|
|
728 | |
|
|
729 | =item $state->is_new |
|
|
730 | |
|
|
731 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
732 | yet. Those states basically consist of only the code reference to call and |
|
|
733 | the arguments, but consumes very little other resources. New states will |
|
|
734 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
735 | |
|
|
736 | =item $state->is_zombie |
|
|
737 | |
|
|
738 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
739 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
740 | C<safe_cancel>'ed or simply went out of scope. |
|
|
741 | |
|
|
742 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
743 | exited and only stores and exit status and no other resources is called a |
|
|
744 | "zombie". |
|
|
745 | |
354 | =item $is_ready = $coroutine->is_ready |
746 | =item $is_ready = $coro->is_ready |
355 | |
747 | |
356 | Return whether the coroutine is currently the ready queue or not, |
748 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
|
|
749 | object gets destroyed, it will eventually be scheduled by the scheduler. |
357 | |
750 | |
|
|
751 | =item $is_running = $coro->is_running |
|
|
752 | |
|
|
753 | Returns true iff the Coro object is currently running. Only one Coro object |
|
|
754 | can ever be in the running state (but it currently is possible to have |
|
|
755 | multiple running Coro::States). |
|
|
756 | |
|
|
757 | =item $is_suspended = $coro->is_suspended |
|
|
758 | |
|
|
759 | Returns true iff this Coro object has been suspended. Suspended Coros will |
|
|
760 | not ever be scheduled. |
|
|
761 | |
358 | =item $coroutine->cancel (arg...) |
762 | =item $coro->cancel (arg...) |
359 | |
763 | |
360 | Terminates the given coroutine and makes it return the given arguments as |
764 | Terminates the given Coro thread and makes it return the given arguments as |
361 | status (default: the empty list). Never returns if the coroutine is the |
765 | status (default: an empty list). Never returns if the Coro is the |
362 | current coroutine. |
766 | current Coro. |
363 | |
767 | |
364 | =cut |
768 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
769 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
770 | bad things can happen, or if the cancelled thread insists on running |
|
|
771 | complicated cleanup handlers that rely on it'S thread context, things will |
|
|
772 | not work. |
365 | |
773 | |
366 | sub cancel { |
774 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
367 | my $self = shift; |
775 | a thread context, and is not allowed to switch to other threads. On the |
|
|
776 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
777 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
778 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
779 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
368 | |
780 | |
369 | if ($current == $self) { |
781 | The arguments to C<< ->cancel >> are not copied, but instead will |
370 | terminate @_; |
782 | be referenced directly (e.g. if you pass C<$var> and after the call |
371 | } else { |
783 | change that variable, then you might change the return values passed to |
372 | $self->{_status} = [@_]; |
784 | e.g. C<join>, so don't do that). |
373 | $self->_cancel; |
785 | |
|
|
786 | The resources of the Coro are usually freed (or destructed) before this |
|
|
787 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
788 | in some cases the manager thread has to run first to actually destruct the |
|
|
789 | Coro object. |
|
|
790 | |
|
|
791 | =item $coro->safe_cancel ($arg...) |
|
|
792 | |
|
|
793 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
794 | consequently, can fail with an exception in cases the thread is not in a |
|
|
795 | cancellable state. |
|
|
796 | |
|
|
797 | This method works a bit like throwing an exception that cannot be caught |
|
|
798 | - specifically, it will clean up the thread from within itself, so |
|
|
799 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
800 | context and can block if they wish. The downside is that there is no |
|
|
801 | guarantee that the thread can be cancelled when you call this method, and |
|
|
802 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
803 | C<terminate>. |
|
|
804 | |
|
|
805 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
806 | or it has no C context attached and is inside an SLF function. |
|
|
807 | |
|
|
808 | The latter two basically mean that the thread isn't currently inside a |
|
|
809 | perl callback called from some C function (usually via some XS modules) |
|
|
810 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
811 | API). |
|
|
812 | |
|
|
813 | This call returns true when it could cancel the thread, or croaks with an |
|
|
814 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
815 | |
|
|
816 | Why the weird interface? Well, there are two common models on how and |
|
|
817 | when to cancel things. In the first, you have the expectation that your |
|
|
818 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
819 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
820 | croaks to notify of the bug. |
|
|
821 | |
|
|
822 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
823 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
824 | relatively easy like this: |
|
|
825 | |
|
|
826 | if (! eval { $coro->safe_cancel }) { |
|
|
827 | warn "unable to cancel thread: $@"; |
374 | } |
828 | } |
375 | } |
|
|
376 | |
829 | |
|
|
830 | However, what you never should do is first try to cancel "safely" and |
|
|
831 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
832 | no sense: either you rely on being able to execute cleanup code in your |
|
|
833 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
834 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
835 | direct. |
|
|
836 | |
377 | =item $coroutine->schedule_to |
837 | =item $coro->schedule_to |
378 | |
838 | |
379 | Puts the current coroutine to sleep (like C<Coro::schedule>), but instead |
839 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
380 | of continuing with the next coro from the ready queue, always switch to |
840 | of continuing with the next coro from the ready queue, always switch to |
381 | the given coroutine object (regardless of priority etc.). The readyness |
841 | the given coro object (regardless of priority etc.). The readyness |
382 | state of that coroutine isn't changed. |
842 | state of that coro isn't changed. |
383 | |
843 | |
384 | This is an advanced method for special cases - I'd love to hear about any |
844 | This is an advanced method for special cases - I'd love to hear about any |
385 | uses for this one. |
845 | uses for this one. |
386 | |
846 | |
387 | =item $coroutine->cede_to |
847 | =item $coro->cede_to |
388 | |
848 | |
389 | Like C<schedule_to>, but puts the current coroutine into the ready |
849 | Like C<schedule_to>, but puts the current coro into the ready |
390 | queue. This has the effect of temporarily switching to the given |
850 | queue. This has the effect of temporarily switching to the given |
391 | coroutine, and continuing some time later. |
851 | coro, and continuing some time later. |
392 | |
852 | |
393 | This is an advanced method for special cases - I'd love to hear about any |
853 | This is an advanced method for special cases - I'd love to hear about any |
394 | uses for this one. |
854 | uses for this one. |
395 | |
855 | |
396 | =item $coroutine->throw ([$scalar]) |
856 | =item $coro->throw ([$scalar]) |
397 | |
857 | |
398 | If C<$throw> is specified and defined, it will be thrown as an exception |
858 | If C<$throw> is specified and defined, it will be thrown as an exception |
399 | inside the coroutine at the next convenient point in time. Otherwise |
859 | inside the coro at the next convenient point in time. Otherwise |
400 | clears the exception object. |
860 | clears the exception object. |
401 | |
861 | |
402 | Coro will check for the exception each time a schedule-like-function |
862 | Coro will check for the exception each time a schedule-like-function |
403 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
863 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
404 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
864 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
405 | detect this case and return early in case an exception is pending. |
865 | that are part of Coro itself) detect this case and return early in case an |
|
|
866 | exception is pending. |
406 | |
867 | |
407 | The exception object will be thrown "as is" with the specified scalar in |
868 | The exception object will be thrown "as is" with the specified scalar in |
408 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
869 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
409 | (unlike with C<die>). |
870 | (unlike with C<die>). |
410 | |
871 | |
411 | This can be used as a softer means than C<cancel> to ask a coroutine to |
872 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
412 | end itself, although there is no guarantee that the exception will lead to |
873 | >to ask a coro to end itself, although there is no guarantee that the |
413 | termination, and if the exception isn't caught it might well end the whole |
874 | exception will lead to termination, and if the exception isn't caught it |
414 | program. |
875 | might well end the whole program. |
415 | |
876 | |
416 | You might also think of C<throw> as being the moral equivalent of |
877 | You might also think of C<throw> as being the moral equivalent of |
417 | C<kill>ing a coroutine with a signal (in this case, a scalar). |
878 | C<kill>ing a coro with a signal (in this case, a scalar). |
418 | |
879 | |
419 | =item $coroutine->join |
880 | =item $coro->join |
420 | |
881 | |
421 | Wait until the coroutine terminates and return any values given to the |
882 | Wait until the coro terminates and return any values given to the |
422 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
883 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
423 | from multiple coroutines, and all will be resumed and given the status |
884 | from multiple threads, and all will be resumed and given the status |
424 | return once the C<$coroutine> terminates. |
885 | return once the C<$coro> terminates. |
425 | |
886 | |
426 | =cut |
|
|
427 | |
|
|
428 | sub join { |
|
|
429 | my $self = shift; |
|
|
430 | |
|
|
431 | unless ($self->{_status}) { |
|
|
432 | my $current = $current; |
|
|
433 | |
|
|
434 | push @{$self->{_on_destroy}}, sub { |
|
|
435 | $current->ready; |
|
|
436 | undef $current; |
|
|
437 | }; |
|
|
438 | |
|
|
439 | &schedule while $current; |
|
|
440 | } |
|
|
441 | |
|
|
442 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
443 | } |
|
|
444 | |
|
|
445 | =item $coroutine->on_destroy (\&cb) |
887 | =item $coro->on_destroy (\&cb) |
446 | |
888 | |
447 | Registers a callback that is called when this coroutine gets destroyed, |
889 | Registers a callback that is called when this coro thread gets destroyed, |
448 | but before it is joined. The callback gets passed the terminate arguments, |
890 | that is, after it's resources have been freed but before it is joined. The |
|
|
891 | callback gets passed the terminate/cancel arguments, if any, and I<must |
449 | if any, and I<must not> die, under any circumstances. |
892 | not> die, under any circumstances. |
450 | |
893 | |
451 | =cut |
894 | There can be any number of C<on_destroy> callbacks per coro, and there is |
|
|
895 | no way currently to remove a callback once added. |
452 | |
896 | |
453 | sub on_destroy { |
|
|
454 | my ($self, $cb) = @_; |
|
|
455 | |
|
|
456 | push @{ $self->{_on_destroy} }, $cb; |
|
|
457 | } |
|
|
458 | |
|
|
459 | =item $oldprio = $coroutine->prio ($newprio) |
897 | =item $oldprio = $coro->prio ($newprio) |
460 | |
898 | |
461 | Sets (or gets, if the argument is missing) the priority of the |
899 | Sets (or gets, if the argument is missing) the priority of the |
462 | coroutine. Higher priority coroutines get run before lower priority |
900 | coro thread. Higher priority coro get run before lower priority |
463 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
901 | coros. Priorities are small signed integers (currently -4 .. +3), |
464 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
902 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
465 | to get then): |
903 | to get then): |
466 | |
904 | |
467 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
905 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
468 | 3 > 1 > 0 > -1 > -3 > -4 |
906 | 3 > 1 > 0 > -1 > -3 > -4 |
469 | |
907 | |
470 | # set priority to HIGH |
908 | # set priority to HIGH |
471 | current->prio(PRIO_HIGH); |
909 | current->prio (PRIO_HIGH); |
472 | |
910 | |
473 | The idle coroutine ($Coro::idle) always has a lower priority than any |
911 | The idle coro thread ($Coro::idle) always has a lower priority than any |
474 | existing coroutine. |
912 | existing coro. |
475 | |
913 | |
476 | Changing the priority of the current coroutine will take effect immediately, |
914 | Changing the priority of the current coro will take effect immediately, |
477 | but changing the priority of coroutines in the ready queue (but not |
915 | but changing the priority of a coro in the ready queue (but not running) |
478 | running) will only take effect after the next schedule (of that |
916 | will only take effect after the next schedule (of that coro). This is a |
479 | coroutine). This is a bug that will be fixed in some future version. |
917 | bug that will be fixed in some future version. |
480 | |
918 | |
481 | =item $newprio = $coroutine->nice ($change) |
919 | =item $newprio = $coro->nice ($change) |
482 | |
920 | |
483 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
921 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
484 | higher values mean lower priority, just as in unix). |
922 | higher values mean lower priority, just as in UNIX's nice command). |
485 | |
923 | |
486 | =item $olddesc = $coroutine->desc ($newdesc) |
924 | =item $olddesc = $coro->desc ($newdesc) |
487 | |
925 | |
488 | Sets (or gets in case the argument is missing) the description for this |
926 | Sets (or gets in case the argument is missing) the description for this |
489 | coroutine. This is just a free-form string you can associate with a |
927 | coro thread. This is just a free-form string you can associate with a |
490 | coroutine. |
928 | coro. |
491 | |
929 | |
492 | This method simply sets the C<< $coroutine->{desc} >> member to the given |
930 | This method simply sets the C<< $coro->{desc} >> member to the given |
493 | string. You can modify this member directly if you wish. |
931 | string. You can modify this member directly if you wish, and in fact, this |
|
|
932 | is often preferred to indicate major processing states that cna then be |
|
|
933 | seen for example in a L<Coro::Debug> session: |
|
|
934 | |
|
|
935 | sub my_long_function { |
|
|
936 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
937 | ... |
|
|
938 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
939 | ... |
|
|
940 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
941 | ... |
|
|
942 | } |
494 | |
943 | |
495 | =cut |
944 | =cut |
496 | |
945 | |
497 | sub desc { |
946 | sub desc { |
498 | my $old = $_[0]{desc}; |
947 | my $old = $_[0]{desc}; |
499 | $_[0]{desc} = $_[1] if @_ > 1; |
948 | $_[0]{desc} = $_[1] if @_ > 1; |
500 | $old; |
949 | $old; |
501 | } |
950 | } |
502 | |
951 | |
|
|
952 | sub transfer { |
|
|
953 | require Carp; |
|
|
954 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
955 | } |
|
|
956 | |
503 | =back |
957 | =back |
504 | |
958 | |
505 | =head2 GLOBAL FUNCTIONS |
959 | =head1 GLOBAL FUNCTIONS |
506 | |
960 | |
507 | =over 4 |
961 | =over 4 |
508 | |
962 | |
509 | =item Coro::nready |
963 | =item Coro::nready |
510 | |
964 | |
511 | Returns the number of coroutines that are currently in the ready state, |
965 | Returns the number of coro that are currently in the ready state, |
512 | i.e. that can be switched to by calling C<schedule> directory or |
966 | i.e. that can be switched to by calling C<schedule> directory or |
513 | indirectly. The value C<0> means that the only runnable coroutine is the |
967 | indirectly. The value C<0> means that the only runnable coro is the |
514 | currently running one, so C<cede> would have no effect, and C<schedule> |
968 | currently running one, so C<cede> would have no effect, and C<schedule> |
515 | would cause a deadlock unless there is an idle handler that wakes up some |
969 | would cause a deadlock unless there is an idle handler that wakes up some |
516 | coroutines. |
970 | coro. |
517 | |
971 | |
518 | =item my $guard = Coro::guard { ... } |
972 | =item my $guard = Coro::guard { ... } |
519 | |
973 | |
520 | This creates and returns a guard object. Nothing happens until the object |
974 | This function still exists, but is deprecated. Please use the |
521 | gets destroyed, in which case the codeblock given as argument will be |
975 | C<Guard::guard> function instead. |
522 | executed. This is useful to free locks or other resources in case of a |
|
|
523 | runtime error or when the coroutine gets canceled, as in both cases the |
|
|
524 | guard block will be executed. The guard object supports only one method, |
|
|
525 | C<< ->cancel >>, which will keep the codeblock from being executed. |
|
|
526 | |
|
|
527 | Example: set some flag and clear it again when the coroutine gets canceled |
|
|
528 | or the function returns: |
|
|
529 | |
|
|
530 | sub do_something { |
|
|
531 | my $guard = Coro::guard { $busy = 0 }; |
|
|
532 | $busy = 1; |
|
|
533 | |
|
|
534 | # do something that requires $busy to be true |
|
|
535 | } |
|
|
536 | |
976 | |
537 | =cut |
977 | =cut |
538 | |
978 | |
539 | sub guard(&) { |
979 | BEGIN { *guard = \&Guard::guard } |
540 | bless \(my $cb = $_[0]), "Coro::guard" |
|
|
541 | } |
|
|
542 | |
|
|
543 | sub Coro::guard::cancel { |
|
|
544 | ${$_[0]} = sub { }; |
|
|
545 | } |
|
|
546 | |
|
|
547 | sub Coro::guard::DESTROY { |
|
|
548 | ${$_[0]}->(); |
|
|
549 | } |
|
|
550 | |
|
|
551 | |
980 | |
552 | =item unblock_sub { ... } |
981 | =item unblock_sub { ... } |
553 | |
982 | |
554 | This utility function takes a BLOCK or code reference and "unblocks" it, |
983 | This utility function takes a BLOCK or code reference and "unblocks" it, |
555 | returning a new coderef. Unblocking means that calling the new coderef |
984 | returning a new coderef. Unblocking means that calling the new coderef |
556 | will return immediately without blocking, returning nothing, while the |
985 | will return immediately without blocking, returning nothing, while the |
557 | original code ref will be called (with parameters) from within another |
986 | original code ref will be called (with parameters) from within another |
558 | coroutine. |
987 | coro. |
559 | |
988 | |
560 | The reason this function exists is that many event libraries (such as the |
989 | The reason this function exists is that many event libraries (such as |
561 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
990 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
562 | of thread-safety). This means you must not block within event callbacks, |
991 | of reentrancy). This means you must not block within event callbacks, |
563 | otherwise you might suffer from crashes or worse. The only event library |
992 | otherwise you might suffer from crashes or worse. The only event library |
564 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
993 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
994 | you might still run into deadlocks if all event loops are blocked). |
|
|
995 | |
|
|
996 | Coro will try to catch you when you block in the event loop |
|
|
997 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
998 | only works when you do not run your own event loop. |
565 | |
999 | |
566 | This function allows your callbacks to block by executing them in another |
1000 | This function allows your callbacks to block by executing them in another |
567 | coroutine where it is safe to block. One example where blocking is handy |
1001 | coro where it is safe to block. One example where blocking is handy |
568 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1002 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
569 | disk, for example. |
1003 | disk, for example. |
570 | |
1004 | |
571 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
1005 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
572 | creating event callbacks that want to block. |
1006 | creating event callbacks that want to block. |
573 | |
1007 | |
574 | If your handler does not plan to block (e.g. simply sends a message to |
1008 | If your handler does not plan to block (e.g. simply sends a message to |
575 | another coroutine, or puts some other coroutine into the ready queue), |
1009 | another coro, or puts some other coro into the ready queue), there is |
576 | there is no reason to use C<unblock_sub>. |
1010 | no reason to use C<unblock_sub>. |
577 | |
1011 | |
578 | Note that you also need to use C<unblock_sub> for any other callbacks that |
1012 | Note that you also need to use C<unblock_sub> for any other callbacks that |
579 | are indirectly executed by any C-based event loop. For example, when you |
1013 | are indirectly executed by any C-based event loop. For example, when you |
580 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
1014 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
581 | provides callbacks that are the result of some event callback, then you |
1015 | provides callbacks that are the result of some event callback, then you |
… | |
… | |
611 | unshift @unblock_queue, [$cb, @_]; |
1045 | unshift @unblock_queue, [$cb, @_]; |
612 | $unblock_scheduler->ready; |
1046 | $unblock_scheduler->ready; |
613 | } |
1047 | } |
614 | } |
1048 | } |
615 | |
1049 | |
616 | =item $cb = Coro::rouse_cb |
1050 | =item $cb = rouse_cb |
617 | |
1051 | |
618 | Create and return a "rouse callback". That's a code reference that, when |
1052 | Create and return a "rouse callback". That's a code reference that, |
619 | called, will save its arguments and notify the owner coroutine of the |
1053 | when called, will remember a copy of its arguments and notify the owner |
620 | callback. |
1054 | coro of the callback. |
621 | |
1055 | |
622 | See the next function. |
1056 | See the next function. |
623 | |
1057 | |
624 | =item @args = Coro::rouse_wait [$cb] |
1058 | =item @args = rouse_wait [$cb] |
625 | |
1059 | |
626 | Wait for the specified rouse callback (or the last one tht was created in |
1060 | Wait for the specified rouse callback (or the last one that was created in |
627 | this coroutine). |
1061 | this coro). |
628 | |
1062 | |
629 | As soon as the callback is invoked (or when the calback was invoked before |
1063 | As soon as the callback is invoked (or when the callback was invoked |
630 | C<rouse_wait>), it will return a copy of the arguments originally passed |
1064 | before C<rouse_wait>), it will return the arguments originally passed to |
631 | to the rouse callback. |
1065 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
1066 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
1067 | statement at the end. |
632 | |
1068 | |
633 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
1069 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
634 | |
1070 | |
635 | =back |
1071 | =back |
636 | |
1072 | |
637 | =cut |
1073 | =cut |
638 | |
1074 | |
|
|
1075 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1076 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1077 | |
|
|
1078 | *{"Coro::$module\::new"} = sub { |
|
|
1079 | require "Coro/$module.pm"; |
|
|
1080 | |
|
|
1081 | # some modules have their new predefined in State.xs, some don't |
|
|
1082 | *{"Coro::$module\::new"} = $old |
|
|
1083 | if $old; |
|
|
1084 | |
|
|
1085 | goto &{"Coro::$module\::new"}; |
|
|
1086 | }; |
|
|
1087 | } |
|
|
1088 | |
639 | 1; |
1089 | 1; |
640 | |
1090 | |
641 | =head1 HOW TO WAIT FOR A CALLBACK |
1091 | =head1 HOW TO WAIT FOR A CALLBACK |
642 | |
1092 | |
643 | It is very common for a coroutine to wait for some callback to be |
1093 | It is very common for a coro to wait for some callback to be |
644 | called. This occurs naturally when you use coroutines in an otherwise |
1094 | called. This occurs naturally when you use coro in an otherwise |
645 | event-based program, or when you use event-based libraries. |
1095 | event-based program, or when you use event-based libraries. |
646 | |
1096 | |
647 | These typically register a callback for some event, and call that callback |
1097 | These typically register a callback for some event, and call that callback |
648 | when the event occured. In a coroutine, however, you typically want to |
1098 | when the event occured. In a coro, however, you typically want to |
649 | just wait for the event, simplyifying things. |
1099 | just wait for the event, simplyifying things. |
650 | |
1100 | |
651 | For example C<< AnyEvent->child >> registers a callback to be called when |
1101 | For example C<< AnyEvent->child >> registers a callback to be called when |
652 | a specific child has exited: |
1102 | a specific child has exited: |
653 | |
1103 | |
654 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
1104 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
655 | |
1105 | |
656 | But from withina coroutine, you often just want to write this: |
1106 | But from within a coro, you often just want to write this: |
657 | |
1107 | |
658 | my $status = wait_for_child $pid; |
1108 | my $status = wait_for_child $pid; |
659 | |
1109 | |
660 | Coro offers two functions specifically designed to make this easy, |
1110 | Coro offers two functions specifically designed to make this easy, |
661 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
1111 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
662 | |
1112 | |
663 | The first function, C<rouse_cb>, generates and returns a callback that, |
1113 | The first function, C<rouse_cb>, generates and returns a callback that, |
664 | when invoked, will save it's arguments and notify the coroutine that |
1114 | when invoked, will save its arguments and notify the coro that |
665 | created the callback. |
1115 | created the callback. |
666 | |
1116 | |
667 | The second function, C<rouse_wait>, waits for the callback to be called |
1117 | The second function, C<rouse_wait>, waits for the callback to be called |
668 | (by calling C<schedule> to go to sleep) and returns the arguments |
1118 | (by calling C<schedule> to go to sleep) and returns the arguments |
669 | originally passed to the callback. |
1119 | originally passed to the callback. |
… | |
… | |
684 | you can roll your own, using C<schedule>: |
1134 | you can roll your own, using C<schedule>: |
685 | |
1135 | |
686 | sub wait_for_child($) { |
1136 | sub wait_for_child($) { |
687 | my ($pid) = @_; |
1137 | my ($pid) = @_; |
688 | |
1138 | |
689 | # store the current coroutine in $current, |
1139 | # store the current coro in $current, |
690 | # and provide result variables for the closure passed to ->child |
1140 | # and provide result variables for the closure passed to ->child |
691 | my $current = $Coro::current; |
1141 | my $current = $Coro::current; |
692 | my ($done, $rstatus); |
1142 | my ($done, $rstatus); |
693 | |
1143 | |
694 | # pass a closure to ->child |
1144 | # pass a closure to ->child |
… | |
… | |
710 | |
1160 | |
711 | =item fork with pthread backend |
1161 | =item fork with pthread backend |
712 | |
1162 | |
713 | When Coro is compiled using the pthread backend (which isn't recommended |
1163 | When Coro is compiled using the pthread backend (which isn't recommended |
714 | but required on many BSDs as their libcs are completely broken), then |
1164 | but required on many BSDs as their libcs are completely broken), then |
715 | coroutines will not survive a fork. There is no known workaround except to |
1165 | coro will not survive a fork. There is no known workaround except to |
716 | fix your libc and use a saner backend. |
1166 | fix your libc and use a saner backend. |
717 | |
1167 | |
718 | =item perl process emulation ("threads") |
1168 | =item perl process emulation ("threads") |
719 | |
1169 | |
720 | This module is not perl-pseudo-thread-safe. You should only ever use this |
1170 | This module is not perl-pseudo-thread-safe. You should only ever use this |
721 | module from the same thread (this requirement might be removed in the |
1171 | module from the first thread (this requirement might be removed in the |
722 | future to allow per-thread schedulers, but Coro::State does not yet allow |
1172 | future to allow per-thread schedulers, but Coro::State does not yet allow |
723 | this). I recommend disabling thread support and using processes, as having |
1173 | this). I recommend disabling thread support and using processes, as having |
724 | the windows process emulation enabled under unix roughly halves perl |
1174 | the windows process emulation enabled under unix roughly halves perl |
725 | performance, even when not used. |
1175 | performance, even when not used. |
726 | |
1176 | |
|
|
1177 | Attempts to use threads created in another emulated process will crash |
|
|
1178 | ("cleanly", with a null pointer exception). |
|
|
1179 | |
727 | =item coroutine switching not signal safe |
1180 | =item coro switching is not signal safe |
728 | |
1181 | |
729 | You must not switch to another coroutine from within a signal handler |
1182 | You must not switch to another coro from within a signal handler (only |
730 | (only relevant with %SIG - most event libraries provide safe signals). |
1183 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1184 | you are sure you are not interrupting a Coro function. |
731 | |
1185 | |
732 | That means you I<MUST NOT> call any function that might "block" the |
1186 | That means you I<MUST NOT> call any function that might "block" the |
733 | current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
1187 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
734 | anything that calls those. Everything else, including calling C<ready>, |
1188 | anything that calls those. Everything else, including calling C<ready>, |
735 | works. |
1189 | works. |
736 | |
1190 | |
737 | =back |
1191 | =back |
738 | |
1192 | |
739 | |
1193 | |
|
|
1194 | =head1 WINDOWS PROCESS EMULATION |
|
|
1195 | |
|
|
1196 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1197 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1198 | while in the same mail making rather confused statements about perl |
|
|
1199 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1200 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1201 | it is probably not obvious to everybody). |
|
|
1202 | |
|
|
1203 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1204 | scripting languages given on the perl workshop 2009: |
|
|
1205 | |
|
|
1206 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1207 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1208 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1209 | |
|
|
1210 | It does that by using threads instead of OS processes. The difference |
|
|
1211 | between processes and threads is that threads share memory (and other |
|
|
1212 | state, such as files) between threads within a single process, while |
|
|
1213 | processes do not share anything (at least not semantically). That |
|
|
1214 | means that modifications done by one thread are seen by others, while |
|
|
1215 | modifications by one process are not seen by other processes. |
|
|
1216 | |
|
|
1217 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1218 | process, all state is copied (memory is copied physically, files and code |
|
|
1219 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1220 | the same behaviour can be achieved by using operating system processes, |
|
|
1221 | except that UNIX typically uses hardware built into the system to do this |
|
|
1222 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1223 | software (rather efficiently, but of course it is still much slower than |
|
|
1224 | dedicated hardware). |
|
|
1225 | |
|
|
1226 | As mentioned before, loading code, modifying code, modifying data |
|
|
1227 | structures and so on is only visible in the ithreads process doing the |
|
|
1228 | modification, not in other ithread processes within the same OS process. |
|
|
1229 | |
|
|
1230 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1231 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1232 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1233 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1234 | faster). |
|
|
1235 | |
|
|
1236 | Sharing data is in the i-threads model is done by transfering data |
|
|
1237 | structures between threads using copying semantics, which is very slow - |
|
|
1238 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1239 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1240 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1241 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1242 | real threads, refer to my talk for details). |
|
|
1243 | |
|
|
1244 | As summary, i-threads *use* threads to implement processes, while |
|
|
1245 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1246 | processes. I-threads slow down every perl program when enabled, and |
|
|
1247 | outside of windows, serve no (or little) practical purpose, but |
|
|
1248 | disadvantages every single-threaded Perl program. |
|
|
1249 | |
|
|
1250 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1251 | misleading as it implies that it implements some kind of thread model for |
|
|
1252 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1253 | actual use and behaviour of it much better. |
|
|
1254 | |
740 | =head1 SEE ALSO |
1255 | =head1 SEE ALSO |
741 | |
1256 | |
742 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
1257 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
743 | |
1258 | |
744 | Debugging: L<Coro::Debug>. |
1259 | Debugging: L<Coro::Debug>. |
745 | |
1260 | |
746 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
1261 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
747 | |
1262 | |
748 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
1263 | Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
1264 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
749 | |
1265 | |
750 | IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
1266 | I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
751 | |
1267 | |
752 | Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>. |
1268 | Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
1269 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
1270 | L<Coro::Select>. |
753 | |
1271 | |
754 | XS API: L<Coro::MakeMaker>. |
1272 | XS API: L<Coro::MakeMaker>. |
755 | |
1273 | |
756 | Low level Configuration, Coroutine Environment: L<Coro::State>. |
1274 | Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
757 | |
1275 | |
758 | =head1 AUTHOR |
1276 | =head1 AUTHOR |
759 | |
1277 | |
760 | Marc Lehmann <schmorp@schmorp.de> |
1278 | Marc Lehmann <schmorp@schmorp.de> |
761 | http://home.schmorp.de/ |
1279 | http://home.schmorp.de/ |