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 | |
9 | async { |
9 | async { |
10 | # some asynchronous thread of execution |
10 | # some asynchronous thread of execution |
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11 | print "2\n"; |
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12 | cede; # yield back to main |
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13 | print "4\n"; |
11 | }; |
14 | }; |
12 | |
15 | print "1\n"; |
13 | # alternatively create an async coroutine like this: |
16 | cede; # yield to coro |
14 | |
17 | print "3\n"; |
15 | sub some_func : Coro { |
18 | cede; # and again |
16 | # some more async code |
19 | |
17 | } |
20 | # use locking |
18 | |
21 | my $lock = new Coro::Semaphore; |
19 | cede; |
22 | my $locked; |
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23 | |
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24 | $lock->down; |
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25 | $locked = 1; |
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26 | $lock->up; |
20 | |
27 | |
21 | =head1 DESCRIPTION |
28 | =head1 DESCRIPTION |
22 | |
29 | |
23 | This module collection manages coroutines. Coroutines are similar |
30 | For a tutorial-style introduction, please read the L<Coro::Intro> |
24 | to threads but don't run in parallel at the same time even on SMP |
31 | manpage. This manpage mainly contains reference information. |
25 | machines. The specific flavor of coroutine use din this module also |
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26 | guarentees you that it will not switch between coroutines unless |
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27 | necessary, at easily-identified points in your program, so locking and |
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28 | parallel access are rarely an issue, making coroutine programming much |
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29 | safer than threads programming. |
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30 | |
32 | |
31 | (Perl, however, does not natively support real threads but instead does a |
33 | This module collection manages continuations in general, most often in |
32 | very slow and memory-intensive emulation of processes using threads. This |
34 | the form of cooperative threads (also called coros, or simply "coro" |
33 | is a performance win on Windows machines, and a loss everywhere else). |
35 | in the documentation). They are similar to kernel threads but don't (in |
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36 | general) run in parallel at the same time even on SMP machines. The |
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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. |
34 | |
42 | |
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43 | Unlike the so-called "Perl threads" (which are not actually real threads |
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44 | but only the windows process emulation (see section of same name for |
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45 | more details) ported to UNIX, and as such act as processes), Coro |
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46 | provides a full shared address space, which makes communication between |
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47 | threads very easy. And coro threads are fast, too: disabling the Windows |
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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. |
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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 | |
35 | In this module, coroutines are defined as "callchain + lexical variables + |
60 | In this module, a thread is defined as "callchain + lexical variables + |
36 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
61 | some package variables + C stack), that is, a thread has its own callchain, |
37 | 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 |
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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 | Yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the coro |
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201 | 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 | Last not least, a coro thread object that isn't referenced is C<< |
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224 | ->cancel >>'ed automatically - just like other objects in Perl. This |
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225 | is not such a common case, however - a running thread is referencedy by |
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226 | C<$Coro::current>, a thread ready to run is referenced by the ready queue, |
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227 | a thread waiting on a lock or semaphore is referenced by being in some |
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228 | wait list and so on. But a thread that isn't in any of those queues gets |
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229 | cancelled: |
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230 | |
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231 | async { |
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232 | schedule; # cede to other coros, don't go into the ready queue |
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233 | }; |
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234 | |
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235 | cede; |
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236 | # now the async above is destroyed, as it is not referenced by anything. |
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237 | |
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238 | A slightly embellished example might make it clearer: |
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239 | |
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240 | async { |
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241 | my $guard = Guard::guard { print "destroyed\n" }; |
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242 | schedule while 1; |
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243 | }; |
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244 | |
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245 | cede; |
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246 | |
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247 | Superficially one might not expect any output - since the C<async> |
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248 | implements an endless loop, the C<$guard> will not be cleaned up. However, |
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249 | since the thread object returned by C<async> is not stored anywhere, the |
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250 | thread is initially referenced because it is in the ready queue, when it |
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251 | runs it is referenced by C<$Coro::current>, but when it calls C<schedule>, |
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252 | it gets C<cancel>ed causing the guard object to be destroyed (see the next |
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253 | section), and printing it's message. |
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254 | |
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255 | If this seems a bit drastic, remember that this only happens when nothing |
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256 | references the thread anymore, which means there is no way to further |
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257 | execute it, ever. The only options at this point are leaking the thread, |
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258 | or cleaning it up, which brings us to... |
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259 | |
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260 | =item 5. Cleanup |
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261 | |
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262 | Threads will allocate various resources. Most but not all will be returned |
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263 | when a thread terminates, during clean-up. |
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264 | |
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265 | Cleanup is quite similar to throwing an uncaught exception: perl will |
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266 | work it's way up through all subroutine calls and blocks. On it's way, it |
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267 | will release all C<my> variables, undo all C<local>'s and free any other |
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268 | resources truly local to the thread. |
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269 | |
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270 | So, a common way to free resources is to keep them referenced only by my |
38 | variables. |
271 | variables: |
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272 | |
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273 | async { |
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274 | my $big_cache = new Cache ...; |
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275 | }; |
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276 | |
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277 | If there are no other references, then the C<$big_cache> object will be |
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278 | freed when the thread terminates, regardless of how it does so. |
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279 | |
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280 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
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281 | resources, but that's where the C<guard> methods come in handy: |
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282 | |
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283 | my $sem = new Coro::Semaphore; |
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284 | |
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285 | async { |
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286 | my $lock_guard = $sem->guard; |
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287 | # if we return, or die or get cancelled, here, |
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288 | # then the semaphore will be "up"ed. |
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289 | }; |
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290 | |
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291 | The C<Guard::guard> function comes in handy for any custom cleanup you |
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292 | might want to do (but you cannot switch to other coroutines from those |
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293 | code blocks): |
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294 | |
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295 | async { |
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296 | my $window = new Gtk2::Window "toplevel"; |
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297 | # The window will not be cleaned up automatically, even when $window |
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298 | # gets freed, so use a guard to ensure it's destruction |
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299 | # in case of an error: |
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300 | my $window_guard = Guard::guard { $window->destroy }; |
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301 | |
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302 | # we are safe here |
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303 | }; |
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304 | |
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305 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
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306 | replacing the coro thread description: |
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307 | |
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308 | sub myfunction { |
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309 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
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310 | |
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311 | # if we return or die here, the description will be restored |
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312 | } |
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313 | |
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314 | =item 6. Viva La Zombie Muerte |
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315 | |
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316 | Even after a thread has terminated and cleaned up its resources, the Coro |
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317 | object still is there and stores the return values of the thread. |
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318 | |
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319 | When there are no other references, it will simply be cleaned up and |
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320 | freed. |
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321 | |
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322 | If there areany references, the Coro object will stay around, and you |
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323 | can call C<< ->join >> as many times as you wish to retrieve the result |
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324 | values: |
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325 | |
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326 | async { |
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327 | print "hi\n"; |
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328 | 1 |
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329 | }; |
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330 | |
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331 | # run the async above, and free everything before returning |
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332 | # from Coro::cede: |
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333 | Coro::cede; |
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334 | |
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335 | { |
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336 | my $coro = async { |
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337 | print "hi\n"; |
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338 | 1 |
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339 | }; |
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340 | |
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341 | # run the async above, and clean up, but do not free the coro |
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342 | # object: |
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343 | Coro::cede; |
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344 | |
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345 | # optionally retrieve the result values |
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346 | my @results = $coro->join; |
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347 | |
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348 | # now $coro goes out of scope, and presumably gets freed |
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349 | }; |
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350 | |
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351 | =back |
39 | |
352 | |
40 | =cut |
353 | =cut |
41 | |
354 | |
42 | package Coro; |
355 | package Coro; |
43 | |
356 | |
44 | use strict; |
357 | use common::sense; |
45 | no warnings "uninitialized"; |
358 | |
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359 | use Carp (); |
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360 | |
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361 | use Guard (); |
46 | |
362 | |
47 | use Coro::State; |
363 | use Coro::State; |
48 | |
364 | |
49 | use base qw(Coro::State Exporter); |
365 | use base qw(Coro::State Exporter); |
50 | |
366 | |
51 | our $idle; # idle handler |
367 | our $idle; # idle handler |
52 | our $main; # main coroutine |
368 | our $main; # main coro |
53 | our $current; # current coroutine |
369 | our $current; # current coro |
54 | |
370 | |
55 | our $VERSION = '3.61'; |
371 | our $VERSION = 6.33; |
56 | |
372 | |
57 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
373 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
58 | our %EXPORT_TAGS = ( |
374 | our %EXPORT_TAGS = ( |
59 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
375 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
60 | ); |
376 | ); |
61 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
377 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
62 | |
378 | |
63 | { |
379 | =head1 GLOBAL VARIABLES |
64 | my @async; |
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65 | my $init; |
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66 | |
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67 | # this way of handling attributes simply is NOT scalable ;() |
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68 | sub import { |
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69 | no strict 'refs'; |
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70 | |
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71 | Coro->export_to_level (1, @_); |
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72 | |
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73 | my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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74 | *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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75 | my ($package, $ref) = (shift, shift); |
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76 | my @attrs; |
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77 | for (@_) { |
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78 | if ($_ eq "Coro") { |
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79 | push @async, $ref; |
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80 | unless ($init++) { |
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81 | eval q{ |
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82 | sub INIT { |
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83 | &async(pop @async) while @async; |
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84 | } |
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85 | }; |
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86 | } |
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87 | } else { |
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88 | push @attrs, $_; |
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89 | } |
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90 | } |
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91 | return $old ? $old->($package, $ref, @attrs) : @attrs; |
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92 | }; |
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93 | } |
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94 | |
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95 | } |
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96 | |
380 | |
97 | =over 4 |
381 | =over 4 |
98 | |
382 | |
99 | =item $main |
383 | =item $Coro::main |
100 | |
384 | |
101 | This coroutine represents the main program. |
385 | This variable stores the Coro object that represents the main |
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386 | program. While you can C<ready> it and do most other things you can do to |
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387 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
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388 | whether you are running in the main program or not. |
102 | |
389 | |
103 | =cut |
390 | =cut |
104 | |
391 | |
105 | $main = new Coro; |
392 | # $main is now being initialised by Coro::State |
106 | |
393 | |
107 | =item $current (or as function: current) |
394 | =item $Coro::current |
108 | |
395 | |
109 | The current coroutine (the last coroutine switched to). The initial value |
396 | The Coro object representing the current coro (the last |
|
|
397 | coro that the Coro scheduler switched to). The initial value is |
110 | is C<$main> (of course). |
398 | C<$Coro::main> (of course). |
111 | |
399 | |
112 | This variable is B<strictly> I<read-only>. It is provided for performance |
400 | This variable is B<strictly> I<read-only>. You can take copies of the |
113 | reasons. If performance is not essentiel you are encouraged to use the |
401 | value stored in it and use it as any other Coro object, but you must |
114 | C<Coro::current> function instead. |
402 | not otherwise modify the variable itself. |
115 | |
403 | |
116 | =cut |
404 | =cut |
117 | |
405 | |
118 | # maybe some other module used Coro::Specific before... |
|
|
119 | $main->{specific} = $current->{specific} |
|
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120 | if $current; |
|
|
121 | |
|
|
122 | _set_current $main; |
|
|
123 | |
|
|
124 | sub current() { $current } |
406 | sub current() { $current } # [DEPRECATED] |
125 | |
407 | |
126 | =item $idle |
408 | =item $Coro::idle |
127 | |
409 | |
128 | A callback that is called whenever the scheduler finds no ready coroutines |
410 | This variable is mainly useful to integrate Coro into event loops. It is |
|
|
411 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
|
|
412 | pretty low-level functionality. |
|
|
413 | |
|
|
414 | This variable stores a Coro object that is put into the ready queue when |
|
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415 | there are no other ready threads (without invoking any ready hooks). |
|
|
416 | |
129 | to run. The default implementation prints "FATAL: deadlock detected" and |
417 | The default implementation dies with "FATAL: deadlock detected.", followed |
130 | exits, because the program has no other way to continue. |
418 | by a thread listing, because the program has no other way to continue. |
131 | |
419 | |
132 | This hook is overwritten by modules such as C<Coro::Timer> and |
420 | This hook is overwritten by modules such as C<Coro::EV> and |
133 | C<Coro::Event> to wait on an external event that hopefully wake up a |
421 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
134 | coroutine so the scheduler can run it. |
422 | coro so the scheduler can run it. |
135 | |
423 | |
136 | Please note that if your callback recursively invokes perl (e.g. for event |
424 | See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
137 | handlers), then it must be prepared to be called recursively. |
|
|
138 | |
425 | |
139 | =cut |
426 | =cut |
140 | |
427 | |
141 | $idle = sub { |
428 | # ||= because other modules could have provided their own by now |
142 | require Carp; |
429 | $idle ||= new Coro sub { |
143 | Carp::croak ("FATAL: deadlock detected"); |
430 | require Coro::Debug; |
|
|
431 | die "FATAL: deadlock detected.\n" |
|
|
432 | . Coro::Debug::ps_listing (); |
144 | }; |
433 | }; |
145 | |
434 | |
146 | sub _cancel { |
|
|
147 | my ($self) = @_; |
|
|
148 | |
|
|
149 | # free coroutine data and mark as destructed |
|
|
150 | $self->_destroy |
|
|
151 | or return; |
|
|
152 | |
|
|
153 | # call all destruction callbacks |
|
|
154 | $_->(@{$self->{status}}) |
|
|
155 | for @{(delete $self->{destroy_cb}) || []}; |
|
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156 | } |
|
|
157 | |
|
|
158 | # this coroutine is necessary because a coroutine |
435 | # this coro is necessary because a coro |
159 | # cannot destroy itself. |
436 | # cannot destroy itself. |
160 | my @destroy; |
437 | our @destroy; |
161 | my $manager; |
438 | our $manager; |
162 | |
439 | |
163 | $manager = new Coro sub { |
440 | $manager = new Coro sub { |
164 | while () { |
441 | while () { |
165 | (shift @destroy)->_cancel |
442 | _destroy shift @destroy |
166 | while @destroy; |
443 | while @destroy; |
167 | |
444 | |
168 | &schedule; |
445 | &schedule; |
169 | } |
446 | } |
170 | }; |
447 | }; |
171 | |
448 | $manager->{desc} = "[coro manager]"; |
172 | $manager->prio (PRIO_MAX); |
449 | $manager->prio (PRIO_MAX); |
173 | |
450 | |
174 | # static methods. not really. |
|
|
175 | |
|
|
176 | =back |
451 | =back |
177 | |
452 | |
178 | =head2 STATIC METHODS |
453 | =head1 SIMPLE CORO CREATION |
179 | |
|
|
180 | Static methods are actually functions that operate on the current coroutine only. |
|
|
181 | |
454 | |
182 | =over 4 |
455 | =over 4 |
183 | |
456 | |
184 | =item async { ... } [@args...] |
457 | =item async { ... } [@args...] |
185 | |
458 | |
186 | Create a new asynchronous coroutine and return it's coroutine object |
459 | Create a new coro and return its Coro object (usually |
187 | (usually unused). When the sub returns the new coroutine is automatically |
460 | unused). The coro will be put into the ready queue, so |
|
|
461 | it will start running automatically on the next scheduler run. |
|
|
462 | |
|
|
463 | The first argument is a codeblock/closure that should be executed in the |
|
|
464 | coro. When it returns argument returns the coro is automatically |
188 | terminated. |
465 | terminated. |
189 | |
466 | |
|
|
467 | The remaining arguments are passed as arguments to the closure. |
|
|
468 | |
|
|
469 | See the C<Coro::State::new> constructor for info about the coro |
|
|
470 | environment in which coro are executed. |
|
|
471 | |
190 | Calling C<exit> in a coroutine will do the same as calling exit outside |
472 | Calling C<exit> in a coro will do the same as calling exit outside |
191 | the coroutine. Likewise, when the coroutine dies, the program will exit, |
473 | the coro. Likewise, when the coro dies, the program will exit, |
192 | just as it would in the main program. |
474 | just as it would in the main program. |
193 | |
475 | |
|
|
476 | If you do not want that, you can provide a default C<die> handler, or |
|
|
477 | simply avoid dieing (by use of C<eval>). |
|
|
478 | |
194 | # create a new coroutine that just prints its arguments |
479 | Example: Create a new coro that just prints its arguments. |
|
|
480 | |
195 | async { |
481 | async { |
196 | print "@_\n"; |
482 | print "@_\n"; |
197 | } 1,2,3,4; |
483 | } 1,2,3,4; |
198 | |
484 | |
|
|
485 | =item async_pool { ... } [@args...] |
|
|
486 | |
|
|
487 | Similar to C<async>, but uses a coro pool, so you should not call |
|
|
488 | terminate or join on it (although you are allowed to), and you get a |
|
|
489 | coro that might have executed other code already (which can be good |
|
|
490 | or bad :). |
|
|
491 | |
|
|
492 | On the plus side, this function is about twice as fast as creating (and |
|
|
493 | destroying) a completely new coro, so if you need a lot of generic |
|
|
494 | coros in quick successsion, use C<async_pool>, not C<async>. |
|
|
495 | |
|
|
496 | The code block is executed in an C<eval> context and a warning will be |
|
|
497 | issued in case of an exception instead of terminating the program, as |
|
|
498 | C<async> does. As the coro is being reused, stuff like C<on_destroy> |
|
|
499 | will not work in the expected way, unless you call terminate or cancel, |
|
|
500 | which somehow defeats the purpose of pooling (but is fine in the |
|
|
501 | exceptional case). |
|
|
502 | |
|
|
503 | The priority will be reset to C<0> after each run, tracing will be |
|
|
504 | disabled, the description will be reset and the default output filehandle |
|
|
505 | gets restored, so you can change all these. Otherwise the coro will |
|
|
506 | be re-used "as-is": most notably if you change other per-coro global |
|
|
507 | stuff such as C<$/> you I<must needs> revert that change, which is most |
|
|
508 | simply done by using local as in: C<< local $/ >>. |
|
|
509 | |
|
|
510 | The idle pool size is limited to C<8> idle coros (this can be |
|
|
511 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
|
|
512 | coros as required. |
|
|
513 | |
|
|
514 | If you are concerned about pooled coros growing a lot because a |
|
|
515 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
|
|
516 | { terminate }> once per second or so to slowly replenish the pool. In |
|
|
517 | addition to that, when the stacks used by a handler grows larger than 32kb |
|
|
518 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
|
|
519 | |
199 | =cut |
520 | =cut |
200 | |
521 | |
201 | sub async(&@) { |
|
|
202 | my $coro = new Coro @_; |
|
|
203 | $coro->ready; |
|
|
204 | $coro |
|
|
205 | } |
|
|
206 | |
|
|
207 | =item async_pool { ... } [@args...] |
|
|
208 | |
|
|
209 | Similar to C<async>, but uses a coroutine pool, so you should not call |
|
|
210 | terminate or join (although you are allowed to), and you get a coroutine |
|
|
211 | that might have executed other code already (which can be good or bad :). |
|
|
212 | |
|
|
213 | Also, the block is executed in an C<eval> context and a warning will be |
|
|
214 | issued in case of an exception instead of terminating the program, as |
|
|
215 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
|
|
216 | will not work in the expected way, unless you call terminate or cancel, |
|
|
217 | which somehow defeats the purpose of pooling. |
|
|
218 | |
|
|
219 | The priority will be reset to C<0> after each job, otherwise the coroutine |
|
|
220 | will be re-used "as-is". |
|
|
221 | |
|
|
222 | The pool size is limited to 8 idle coroutines (this can be adjusted by |
|
|
223 | changing $Coro::POOL_SIZE), and there can be as many non-idle coros as |
|
|
224 | required. |
|
|
225 | |
|
|
226 | If you are concerned about pooled coroutines growing a lot because a |
|
|
227 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool { |
|
|
228 | terminate }> once per second or so to slowly replenish the pool. |
|
|
229 | |
|
|
230 | =cut |
|
|
231 | |
|
|
232 | our $POOL_SIZE = 8; |
522 | our $POOL_SIZE = 8; |
|
|
523 | our $POOL_RSS = 32 * 1024; |
233 | our @pool; |
524 | our @async_pool; |
234 | |
525 | |
235 | sub pool_handler { |
526 | sub pool_handler { |
236 | while () { |
527 | while () { |
237 | eval { |
528 | eval { |
238 | my ($cb, @arg) = @{ delete $current->{_invoke} or return }; |
529 | &{&_pool_handler} while 1; |
239 | $cb->(@arg); |
|
|
240 | }; |
530 | }; |
|
|
531 | |
241 | warn $@ if $@; |
532 | warn $@ if $@; |
242 | |
|
|
243 | last if @pool >= $POOL_SIZE; |
|
|
244 | push @pool, $current; |
|
|
245 | |
|
|
246 | $current->save (Coro::State::SAVE_DEF); |
|
|
247 | $current->prio (0); |
|
|
248 | schedule; |
|
|
249 | } |
533 | } |
250 | } |
534 | } |
251 | |
535 | |
252 | sub async_pool(&@) { |
536 | =back |
253 | # this is also inlined into the unlock_scheduler |
|
|
254 | my $coro = (pop @pool or new Coro \&pool_handler); |
|
|
255 | |
537 | |
256 | $coro->{_invoke} = [@_]; |
538 | =head1 STATIC METHODS |
257 | $coro->ready; |
|
|
258 | |
539 | |
259 | $coro |
540 | Static methods are actually functions that implicitly operate on the |
|
|
541 | current coro. |
|
|
542 | |
|
|
543 | =over 4 |
|
|
544 | |
|
|
545 | =item schedule |
|
|
546 | |
|
|
547 | Calls the scheduler. The scheduler will find the next coro that is |
|
|
548 | to be run from the ready queue and switches to it. The next coro |
|
|
549 | to be run is simply the one with the highest priority that is longest |
|
|
550 | in its ready queue. If there is no coro ready, it will call the |
|
|
551 | C<$Coro::idle> hook. |
|
|
552 | |
|
|
553 | Please note that the current coro will I<not> be put into the ready |
|
|
554 | queue, so calling this function usually means you will never be called |
|
|
555 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
|
|
556 | thus waking you up. |
|
|
557 | |
|
|
558 | This makes C<schedule> I<the> generic method to use to block the current |
|
|
559 | coro and wait for events: first you remember the current coro in |
|
|
560 | a variable, then arrange for some callback of yours to call C<< ->ready |
|
|
561 | >> on that once some event happens, and last you call C<schedule> to put |
|
|
562 | yourself to sleep. Note that a lot of things can wake your coro up, |
|
|
563 | so you need to check whether the event indeed happened, e.g. by storing the |
|
|
564 | status in a variable. |
|
|
565 | |
|
|
566 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
|
|
567 | |
|
|
568 | =item cede |
|
|
569 | |
|
|
570 | "Cede" to other coros. This function puts the current coro into |
|
|
571 | the ready queue and calls C<schedule>, which has the effect of giving |
|
|
572 | up the current "timeslice" to other coros of the same or higher |
|
|
573 | priority. Once your coro gets its turn again it will automatically be |
|
|
574 | resumed. |
|
|
575 | |
|
|
576 | This function is often called C<yield> in other languages. |
|
|
577 | |
|
|
578 | =item Coro::cede_notself |
|
|
579 | |
|
|
580 | Works like cede, but is not exported by default and will cede to I<any> |
|
|
581 | coro, regardless of priority. This is useful sometimes to ensure |
|
|
582 | progress is made. |
|
|
583 | |
|
|
584 | =item terminate [arg...] |
|
|
585 | |
|
|
586 | Terminates the current coro with the given status values (see |
|
|
587 | L<cancel>). The values will not be copied, but referenced directly. |
|
|
588 | |
|
|
589 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
|
|
590 | |
|
|
591 | These function install enter and leave winders in the current scope. The |
|
|
592 | enter block will be executed when on_enter is called and whenever the |
|
|
593 | current coro is re-entered by the scheduler, while the leave block is |
|
|
594 | executed whenever the current coro is blocked by the scheduler, and |
|
|
595 | also when the containing scope is exited (by whatever means, be it exit, |
|
|
596 | die, last etc.). |
|
|
597 | |
|
|
598 | I<Neither invoking the scheduler, nor exceptions, are allowed within those |
|
|
599 | BLOCKs>. That means: do not even think about calling C<die> without an |
|
|
600 | eval, and do not even think of entering the scheduler in any way. |
|
|
601 | |
|
|
602 | Since both BLOCKs are tied to the current scope, they will automatically |
|
|
603 | be removed when the current scope exits. |
|
|
604 | |
|
|
605 | These functions implement the same concept as C<dynamic-wind> in scheme |
|
|
606 | does, and are useful when you want to localise some resource to a specific |
|
|
607 | coro. |
|
|
608 | |
|
|
609 | They slow down thread switching considerably for coros that use them |
|
|
610 | (about 40% for a BLOCK with a single assignment, so thread switching is |
|
|
611 | still reasonably fast if the handlers are fast). |
|
|
612 | |
|
|
613 | These functions are best understood by an example: The following function |
|
|
614 | will change the current timezone to "Antarctica/South_Pole", which |
|
|
615 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
|
|
616 | which remember/change the current timezone and restore the previous |
|
|
617 | value, respectively, the timezone is only changed for the coro that |
|
|
618 | installed those handlers. |
|
|
619 | |
|
|
620 | use POSIX qw(tzset); |
|
|
621 | |
|
|
622 | async { |
|
|
623 | my $old_tz; # store outside TZ value here |
|
|
624 | |
|
|
625 | Coro::on_enter { |
|
|
626 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
627 | |
|
|
628 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
|
629 | tzset; # enable new value |
|
|
630 | }; |
|
|
631 | |
|
|
632 | Coro::on_leave { |
|
|
633 | $ENV{TZ} = $old_tz; |
|
|
634 | tzset; # restore old value |
|
|
635 | }; |
|
|
636 | |
|
|
637 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
638 | # without disturbing the TZ of any other coro. |
|
|
639 | }; |
|
|
640 | |
|
|
641 | This can be used to localise about any resource (locale, uid, current |
|
|
642 | working directory etc.) to a block, despite the existance of other |
|
|
643 | coros. |
|
|
644 | |
|
|
645 | Another interesting example implements time-sliced multitasking using |
|
|
646 | interval timers (this could obviously be optimised, but does the job): |
|
|
647 | |
|
|
648 | # "timeslice" the given block |
|
|
649 | sub timeslice(&) { |
|
|
650 | use Time::HiRes (); |
|
|
651 | |
|
|
652 | Coro::on_enter { |
|
|
653 | # on entering the thread, we set an VTALRM handler to cede |
|
|
654 | $SIG{VTALRM} = sub { cede }; |
|
|
655 | # and then start the interval timer |
|
|
656 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
657 | }; |
|
|
658 | Coro::on_leave { |
|
|
659 | # on leaving the thread, we stop the interval timer again |
|
|
660 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
661 | }; |
|
|
662 | |
|
|
663 | &{+shift}; |
|
|
664 | } |
|
|
665 | |
|
|
666 | # use like this: |
|
|
667 | timeslice { |
|
|
668 | # The following is an endless loop that would normally |
|
|
669 | # monopolise the process. Since it runs in a timesliced |
|
|
670 | # environment, it will regularly cede to other threads. |
|
|
671 | while () { } |
|
|
672 | }; |
|
|
673 | |
|
|
674 | |
|
|
675 | =item killall |
|
|
676 | |
|
|
677 | Kills/terminates/cancels all coros except the currently running one. |
|
|
678 | |
|
|
679 | Note that while this will try to free some of the main interpreter |
|
|
680 | resources if the calling coro isn't the main coro, but one |
|
|
681 | cannot free all of them, so if a coro that is not the main coro |
|
|
682 | calls this function, there will be some one-time resource leak. |
|
|
683 | |
|
|
684 | =cut |
|
|
685 | |
|
|
686 | sub killall { |
|
|
687 | for (Coro::State::list) { |
|
|
688 | $_->cancel |
|
|
689 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
|
|
690 | } |
260 | } |
691 | } |
261 | |
692 | |
262 | =item schedule |
693 | =back |
263 | |
694 | |
264 | Calls the scheduler. Please note that the current coroutine will not be put |
695 | =head1 CORO OBJECT METHODS |
265 | into the ready queue, so calling this function usually means you will |
|
|
266 | never be called again unless something else (e.g. an event handler) calls |
|
|
267 | ready. |
|
|
268 | |
696 | |
269 | The canonical way to wait on external events is this: |
697 | These are the methods you can call on coro objects (or to create |
|
|
698 | them). |
270 | |
699 | |
271 | { |
700 | =over 4 |
272 | # remember current coroutine |
|
|
273 | my $current = $Coro::current; |
|
|
274 | |
701 | |
275 | # register a hypothetical event handler |
702 | =item new Coro \&sub [, @args...] |
276 | on_event_invoke sub { |
|
|
277 | # wake up sleeping coroutine |
|
|
278 | $current->ready; |
|
|
279 | undef $current; |
|
|
280 | }; |
|
|
281 | |
703 | |
282 | # call schedule until event occured. |
704 | Create a new coro and return it. When the sub returns, the coro |
283 | # in case we are woken up for other reasons |
705 | automatically terminates as if C<terminate> with the returned values were |
284 | # (current still defined), loop. |
706 | called. To make the coro run you must first put it into the ready |
285 | Coro::schedule while $current; |
707 | queue by calling the ready method. |
286 | } |
|
|
287 | |
708 | |
288 | =item cede |
709 | See C<async> and C<Coro::State::new> for additional info about the |
289 | |
710 | coro environment. |
290 | "Cede" to other coroutines. This function puts the current coroutine into the |
|
|
291 | ready queue and calls C<schedule>, which has the effect of giving up the |
|
|
292 | current "timeslice" to other coroutines of the same or higher priority. |
|
|
293 | |
|
|
294 | Returns true if at least one coroutine switch has happened. |
|
|
295 | |
|
|
296 | =item Coro::cede_notself |
|
|
297 | |
|
|
298 | Works like cede, but is not exported by default and will cede to any |
|
|
299 | coroutine, regardless of priority, once. |
|
|
300 | |
|
|
301 | Returns true if at least one coroutine switch has happened. |
|
|
302 | |
|
|
303 | =item terminate [arg...] |
|
|
304 | |
|
|
305 | Terminates the current coroutine with the given status values (see L<cancel>). |
|
|
306 | |
711 | |
307 | =cut |
712 | =cut |
308 | |
713 | |
309 | sub terminate { |
714 | sub _coro_run { |
310 | $current->cancel (@_); |
|
|
311 | } |
|
|
312 | |
|
|
313 | =back |
|
|
314 | |
|
|
315 | # dynamic methods |
|
|
316 | |
|
|
317 | =head2 COROUTINE METHODS |
|
|
318 | |
|
|
319 | These are the methods you can call on coroutine objects. |
|
|
320 | |
|
|
321 | =over 4 |
|
|
322 | |
|
|
323 | =item new Coro \&sub [, @args...] |
|
|
324 | |
|
|
325 | Create a new coroutine and return it. When the sub returns the coroutine |
|
|
326 | automatically terminates as if C<terminate> with the returned values were |
|
|
327 | called. To make the coroutine run you must first put it into the ready queue |
|
|
328 | by calling the ready method. |
|
|
329 | |
|
|
330 | See C<async> for additional discussion. |
|
|
331 | |
|
|
332 | =cut |
|
|
333 | |
|
|
334 | sub _run_coro { |
|
|
335 | terminate &{+shift}; |
715 | terminate &{+shift}; |
336 | } |
716 | } |
337 | |
717 | |
338 | sub new { |
|
|
339 | my $class = shift; |
|
|
340 | |
|
|
341 | $class->SUPER::new (\&_run_coro, @_) |
|
|
342 | } |
|
|
343 | |
|
|
344 | =item $success = $coroutine->ready |
718 | =item $success = $coro->ready |
345 | |
719 | |
346 | Put the given coroutine into the ready queue (according to it's priority) |
720 | Put the given coro into the end of its ready queue (there is one |
347 | and return true. If the coroutine is already in the ready queue, do nothing |
721 | queue for each priority) and return true. If the coro is already in |
348 | and return false. |
722 | the ready queue, do nothing and return false. |
349 | |
723 | |
|
|
724 | This ensures that the scheduler will resume this coro automatically |
|
|
725 | once all the coro of higher priority and all coro of the same |
|
|
726 | priority that were put into the ready queue earlier have been resumed. |
|
|
727 | |
|
|
728 | =item $coro->suspend |
|
|
729 | |
|
|
730 | Suspends the specified coro. A suspended coro works just like any other |
|
|
731 | coro, except that the scheduler will not select a suspended coro for |
|
|
732 | execution. |
|
|
733 | |
|
|
734 | Suspending a coro can be useful when you want to keep the coro from |
|
|
735 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
736 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
737 | |
|
|
738 | A scenario for the former would be to suspend all (other) coros after a |
|
|
739 | fork and keep them alive, so their destructors aren't called, but new |
|
|
740 | coros can be created. |
|
|
741 | |
|
|
742 | =item $coro->resume |
|
|
743 | |
|
|
744 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
745 | the coro was in the ready queue when it was suspended, it might have been |
|
|
746 | unreadied by the scheduler, so an activation might have been lost. |
|
|
747 | |
|
|
748 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
749 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
750 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
751 | that. |
|
|
752 | |
|
|
753 | =item $state->is_new |
|
|
754 | |
|
|
755 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
756 | yet. Those states basically consist of only the code reference to call and |
|
|
757 | the arguments, but consumes very little other resources. New states will |
|
|
758 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
759 | |
|
|
760 | =item $state->is_zombie |
|
|
761 | |
|
|
762 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
763 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
764 | C<safe_cancel>'ed or simply went out of scope. |
|
|
765 | |
|
|
766 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
767 | exited and only stores and exit status and no other resources is called a |
|
|
768 | "zombie". |
|
|
769 | |
350 | =item $is_ready = $coroutine->is_ready |
770 | =item $is_ready = $coro->is_ready |
351 | |
771 | |
352 | Return wether the coroutine is currently the ready queue or not, |
772 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
|
|
773 | object gets destroyed, it will eventually be scheduled by the scheduler. |
353 | |
774 | |
|
|
775 | =item $is_running = $coro->is_running |
|
|
776 | |
|
|
777 | Returns true iff the Coro object is currently running. Only one Coro object |
|
|
778 | can ever be in the running state (but it currently is possible to have |
|
|
779 | multiple running Coro::States). |
|
|
780 | |
|
|
781 | =item $is_suspended = $coro->is_suspended |
|
|
782 | |
|
|
783 | Returns true iff this Coro object has been suspended. Suspended Coros will |
|
|
784 | not ever be scheduled. |
|
|
785 | |
354 | =item $coroutine->cancel (arg...) |
786 | =item $coro->cancel (arg...) |
355 | |
787 | |
356 | Terminates the given coroutine and makes it return the given arguments as |
788 | Terminates the given Coro thread and makes it return the given arguments as |
357 | status (default: the empty list). Never returns if the coroutine is the |
789 | status (default: an empty list). Never returns if the Coro is the |
358 | current coroutine. |
790 | current Coro. |
359 | |
791 | |
360 | =cut |
792 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
793 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
794 | bad things can happen, or if the cancelled thread insists on running |
|
|
795 | complicated cleanup handlers that rely on its thread context, things will |
|
|
796 | not work. |
361 | |
797 | |
362 | sub cancel { |
798 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
363 | my $self = shift; |
799 | a thread context, and is not allowed to switch to other threads. On the |
364 | $self->{status} = [@_]; |
800 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
801 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
802 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
803 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
365 | |
804 | |
366 | if ($current == $self) { |
805 | The arguments to C<< ->cancel >> are not copied, but instead will |
367 | push @destroy, $self; |
806 | be referenced directly (e.g. if you pass C<$var> and after the call |
368 | $manager->ready; |
807 | change that variable, then you might change the return values passed to |
369 | &schedule while 1; |
808 | e.g. C<join>, so don't do that). |
370 | } else { |
809 | |
371 | $self->_cancel; |
810 | The resources of the Coro are usually freed (or destructed) before this |
|
|
811 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
812 | in some cases the manager thread has to run first to actually destruct the |
|
|
813 | Coro object. |
|
|
814 | |
|
|
815 | =item $coro->safe_cancel ($arg...) |
|
|
816 | |
|
|
817 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
818 | consequently, can fail with an exception in cases the thread is not in a |
|
|
819 | cancellable state. |
|
|
820 | |
|
|
821 | This method works a bit like throwing an exception that cannot be caught |
|
|
822 | - specifically, it will clean up the thread from within itself, so |
|
|
823 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
824 | context and can block if they wish. The downside is that there is no |
|
|
825 | guarantee that the thread can be cancelled when you call this method, and |
|
|
826 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
827 | C<terminate>. |
|
|
828 | |
|
|
829 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
830 | or it has no C context attached and is inside an SLF function. |
|
|
831 | |
|
|
832 | The latter two basically mean that the thread isn't currently inside a |
|
|
833 | perl callback called from some C function (usually via some XS modules) |
|
|
834 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
835 | API). |
|
|
836 | |
|
|
837 | This call returns true when it could cancel the thread, or croaks with an |
|
|
838 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
839 | |
|
|
840 | Why the weird interface? Well, there are two common models on how and |
|
|
841 | when to cancel things. In the first, you have the expectation that your |
|
|
842 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
843 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
844 | croaks to notify of the bug. |
|
|
845 | |
|
|
846 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
847 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
848 | relatively easy like this: |
|
|
849 | |
|
|
850 | if (! eval { $coro->safe_cancel }) { |
|
|
851 | warn "unable to cancel thread: $@"; |
372 | } |
852 | } |
373 | } |
|
|
374 | |
853 | |
|
|
854 | However, what you never should do is first try to cancel "safely" and |
|
|
855 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
856 | no sense: either you rely on being able to execute cleanup code in your |
|
|
857 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
858 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
859 | direct. |
|
|
860 | |
|
|
861 | =item $coro->schedule_to |
|
|
862 | |
|
|
863 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
|
|
864 | of continuing with the next coro from the ready queue, always switch to |
|
|
865 | the given coro object (regardless of priority etc.). The readyness |
|
|
866 | state of that coro isn't changed. |
|
|
867 | |
|
|
868 | This is an advanced method for special cases - I'd love to hear about any |
|
|
869 | uses for this one. |
|
|
870 | |
|
|
871 | =item $coro->cede_to |
|
|
872 | |
|
|
873 | Like C<schedule_to>, but puts the current coro into the ready |
|
|
874 | queue. This has the effect of temporarily switching to the given |
|
|
875 | coro, and continuing some time later. |
|
|
876 | |
|
|
877 | This is an advanced method for special cases - I'd love to hear about any |
|
|
878 | uses for this one. |
|
|
879 | |
|
|
880 | =item $coro->throw ([$scalar]) |
|
|
881 | |
|
|
882 | If C<$throw> is specified and defined, it will be thrown as an exception |
|
|
883 | inside the coro at the next convenient point in time. Otherwise |
|
|
884 | clears the exception object. |
|
|
885 | |
|
|
886 | Coro will check for the exception each time a schedule-like-function |
|
|
887 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
|
|
888 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
|
|
889 | that are part of Coro itself) detect this case and return early in case an |
|
|
890 | exception is pending. |
|
|
891 | |
|
|
892 | The exception object will be thrown "as is" with the specified scalar in |
|
|
893 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
|
|
894 | (unlike with C<die>). |
|
|
895 | |
|
|
896 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
|
|
897 | >to ask a coro to end itself, although there is no guarantee that the |
|
|
898 | exception will lead to termination, and if the exception isn't caught it |
|
|
899 | might well end the whole program. |
|
|
900 | |
|
|
901 | You might also think of C<throw> as being the moral equivalent of |
|
|
902 | C<kill>ing a coro with a signal (in this case, a scalar). |
|
|
903 | |
375 | =item $coroutine->join |
904 | =item $coro->join |
376 | |
905 | |
377 | Wait until the coroutine terminates and return any values given to the |
906 | Wait until the coro terminates and return any values given to the |
378 | C<terminate> or C<cancel> functions. C<join> can be called multiple times |
907 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
379 | from multiple coroutine. |
908 | from multiple threads, and all will be resumed and given the status |
|
|
909 | return once the C<$coro> terminates. |
380 | |
910 | |
381 | =cut |
|
|
382 | |
|
|
383 | sub join { |
|
|
384 | my $self = shift; |
|
|
385 | |
|
|
386 | unless ($self->{status}) { |
|
|
387 | my $current = $current; |
|
|
388 | |
|
|
389 | push @{$self->{destroy_cb}}, sub { |
|
|
390 | $current->ready; |
|
|
391 | undef $current; |
|
|
392 | }; |
|
|
393 | |
|
|
394 | &schedule while $current; |
|
|
395 | } |
|
|
396 | |
|
|
397 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
|
|
398 | } |
|
|
399 | |
|
|
400 | =item $coroutine->on_destroy (\&cb) |
911 | =item $coro->on_destroy (\&cb) |
401 | |
912 | |
402 | Registers a callback that is called when this coroutine gets destroyed, |
913 | Registers a callback that is called when this coro thread gets destroyed, |
403 | but before it is joined. The callback gets passed the terminate arguments, |
914 | that is, after it's resources have been freed but before it is joined. The |
404 | if any. |
915 | callback gets passed the terminate/cancel arguments, if any, and I<must |
|
|
916 | not> die, under any circumstances. |
405 | |
917 | |
406 | =cut |
918 | There can be any number of C<on_destroy> callbacks per coro, and there is |
|
|
919 | no way currently to remove a callback once added. |
407 | |
920 | |
408 | sub on_destroy { |
|
|
409 | my ($self, $cb) = @_; |
|
|
410 | |
|
|
411 | push @{ $self->{destroy_cb} }, $cb; |
|
|
412 | } |
|
|
413 | |
|
|
414 | =item $oldprio = $coroutine->prio ($newprio) |
921 | =item $oldprio = $coro->prio ($newprio) |
415 | |
922 | |
416 | Sets (or gets, if the argument is missing) the priority of the |
923 | Sets (or gets, if the argument is missing) the priority of the |
417 | coroutine. Higher priority coroutines get run before lower priority |
924 | coro thread. Higher priority coro get run before lower priority |
418 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
925 | coros. Priorities are small signed integers (currently -4 .. +3), |
419 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
926 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
420 | to get then): |
927 | to get then): |
421 | |
928 | |
422 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
929 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
423 | 3 > 1 > 0 > -1 > -3 > -4 |
930 | 3 > 1 > 0 > -1 > -3 > -4 |
424 | |
931 | |
425 | # set priority to HIGH |
932 | # set priority to HIGH |
426 | current->prio(PRIO_HIGH); |
933 | current->prio (PRIO_HIGH); |
427 | |
934 | |
428 | The idle coroutine ($Coro::idle) always has a lower priority than any |
935 | The idle coro thread ($Coro::idle) always has a lower priority than any |
429 | existing coroutine. |
936 | existing coro. |
430 | |
937 | |
431 | Changing the priority of the current coroutine will take effect immediately, |
938 | Changing the priority of the current coro will take effect immediately, |
432 | but changing the priority of coroutines in the ready queue (but not |
939 | but changing the priority of a coro in the ready queue (but not running) |
433 | running) will only take effect after the next schedule (of that |
940 | will only take effect after the next schedule (of that coro). This is a |
434 | coroutine). This is a bug that will be fixed in some future version. |
941 | bug that will be fixed in some future version. |
435 | |
942 | |
436 | =item $newprio = $coroutine->nice ($change) |
943 | =item $newprio = $coro->nice ($change) |
437 | |
944 | |
438 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
945 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
439 | higher values mean lower priority, just as in unix). |
946 | higher values mean lower priority, just as in UNIX's nice command). |
440 | |
947 | |
441 | =item $olddesc = $coroutine->desc ($newdesc) |
948 | =item $olddesc = $coro->desc ($newdesc) |
442 | |
949 | |
443 | Sets (or gets in case the argument is missing) the description for this |
950 | Sets (or gets in case the argument is missing) the description for this |
444 | coroutine. This is just a free-form string you can associate with a coroutine. |
951 | coro thread. This is just a free-form string you can associate with a |
|
|
952 | coro. |
|
|
953 | |
|
|
954 | This method simply sets the C<< $coro->{desc} >> member to the given |
|
|
955 | string. You can modify this member directly if you wish, and in fact, this |
|
|
956 | is often preferred to indicate major processing states that can then be |
|
|
957 | seen for example in a L<Coro::Debug> session: |
|
|
958 | |
|
|
959 | sub my_long_function { |
|
|
960 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
961 | ... |
|
|
962 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
963 | ... |
|
|
964 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
965 | ... |
|
|
966 | } |
445 | |
967 | |
446 | =cut |
968 | =cut |
447 | |
969 | |
448 | sub desc { |
970 | sub desc { |
449 | my $old = $_[0]{desc}; |
971 | my $old = $_[0]{desc}; |
450 | $_[0]{desc} = $_[1] if @_ > 1; |
972 | $_[0]{desc} = $_[1] if @_ > 1; |
451 | $old; |
973 | $old; |
452 | } |
974 | } |
453 | |
975 | |
|
|
976 | sub transfer { |
|
|
977 | require Carp; |
|
|
978 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
979 | } |
|
|
980 | |
454 | =back |
981 | =back |
455 | |
982 | |
456 | =head2 GLOBAL FUNCTIONS |
983 | =head1 GLOBAL FUNCTIONS |
457 | |
984 | |
458 | =over 4 |
985 | =over 4 |
459 | |
986 | |
460 | =item Coro::nready |
987 | =item Coro::nready |
461 | |
988 | |
462 | Returns the number of coroutines that are currently in the ready state, |
989 | Returns the number of coro that are currently in the ready state, |
463 | i.e. that can be swicthed to. The value C<0> means that the only runnable |
990 | i.e. that can be switched to by calling C<schedule> directory or |
|
|
991 | indirectly. The value C<0> means that the only runnable coro is the |
464 | coroutine is the currently running one, so C<cede> would have no effect, |
992 | currently running one, so C<cede> would have no effect, and C<schedule> |
465 | and C<schedule> would cause a deadlock unless there is an idle handler |
993 | would cause a deadlock unless there is an idle handler that wakes up some |
466 | that wakes up some coroutines. |
994 | coro. |
467 | |
995 | |
468 | =item my $guard = Coro::guard { ... } |
996 | =item my $guard = Coro::guard { ... } |
469 | |
997 | |
470 | This creates and returns a guard object. Nothing happens until the object |
998 | This function still exists, but is deprecated. Please use the |
471 | gets destroyed, in which case the codeblock given as argument will be |
999 | C<Guard::guard> function instead. |
472 | executed. This is useful to free locks or other resources in case of a |
|
|
473 | runtime error or when the coroutine gets canceled, as in both cases the |
|
|
474 | guard block will be executed. The guard object supports only one method, |
|
|
475 | C<< ->cancel >>, which will keep the codeblock from being executed. |
|
|
476 | |
|
|
477 | Example: set some flag and clear it again when the coroutine gets canceled |
|
|
478 | or the function returns: |
|
|
479 | |
|
|
480 | sub do_something { |
|
|
481 | my $guard = Coro::guard { $busy = 0 }; |
|
|
482 | $busy = 1; |
|
|
483 | |
|
|
484 | # do something that requires $busy to be true |
|
|
485 | } |
|
|
486 | |
1000 | |
487 | =cut |
1001 | =cut |
488 | |
1002 | |
489 | sub guard(&) { |
1003 | BEGIN { *guard = \&Guard::guard } |
490 | bless \(my $cb = $_[0]), "Coro::guard" |
|
|
491 | } |
|
|
492 | |
|
|
493 | sub Coro::guard::cancel { |
|
|
494 | ${$_[0]} = sub { }; |
|
|
495 | } |
|
|
496 | |
|
|
497 | sub Coro::guard::DESTROY { |
|
|
498 | ${$_[0]}->(); |
|
|
499 | } |
|
|
500 | |
|
|
501 | |
1004 | |
502 | =item unblock_sub { ... } |
1005 | =item unblock_sub { ... } |
503 | |
1006 | |
504 | This utility function takes a BLOCK or code reference and "unblocks" it, |
1007 | This utility function takes a BLOCK or code reference and "unblocks" it, |
505 | returning the new coderef. This means that the new coderef will return |
1008 | returning a new coderef. Unblocking means that calling the new coderef |
506 | immediately without blocking, returning nothing, while the original code |
1009 | will return immediately without blocking, returning nothing, while the |
507 | ref will be called (with parameters) from within its own coroutine. |
1010 | original code ref will be called (with parameters) from within another |
|
|
1011 | coro. |
508 | |
1012 | |
509 | The reason this fucntion exists is that many event libraries (such as the |
1013 | The reason this function exists is that many event libraries (such as |
510 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
1014 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
511 | of thread-safety). This means you must not block within event callbacks, |
1015 | of reentrancy). This means you must not block within event callbacks, |
512 | otherwise you might suffer from crashes or worse. |
1016 | otherwise you might suffer from crashes or worse. The only event library |
|
|
1017 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
1018 | you might still run into deadlocks if all event loops are blocked). |
|
|
1019 | |
|
|
1020 | Coro will try to catch you when you block in the event loop |
|
|
1021 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
1022 | only works when you do not run your own event loop. |
513 | |
1023 | |
514 | This function allows your callbacks to block by executing them in another |
1024 | This function allows your callbacks to block by executing them in another |
515 | coroutine where it is safe to block. One example where blocking is handy |
1025 | coro where it is safe to block. One example where blocking is handy |
516 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1026 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
517 | disk. |
1027 | disk, for example. |
518 | |
1028 | |
519 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
1029 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
520 | creating event callbacks that want to block. |
1030 | creating event callbacks that want to block. |
|
|
1031 | |
|
|
1032 | If your handler does not plan to block (e.g. simply sends a message to |
|
|
1033 | another coro, or puts some other coro into the ready queue), there is |
|
|
1034 | no reason to use C<unblock_sub>. |
|
|
1035 | |
|
|
1036 | Note that you also need to use C<unblock_sub> for any other callbacks that |
|
|
1037 | are indirectly executed by any C-based event loop. For example, when you |
|
|
1038 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
|
|
1039 | provides callbacks that are the result of some event callback, then you |
|
|
1040 | must not block either, or use C<unblock_sub>. |
521 | |
1041 | |
522 | =cut |
1042 | =cut |
523 | |
1043 | |
524 | our @unblock_queue; |
1044 | our @unblock_queue; |
525 | |
1045 | |
526 | # we create a special coro because we want to cede, |
1046 | # we create a special coro because we want to cede, |
527 | # to reduce pressure on the coro pool (because most callbacks |
1047 | # to reduce pressure on the coro pool (because most callbacks |
528 | # return immediately and can be reused) and because we cannot cede |
1048 | # return immediately and can be reused) and because we cannot cede |
529 | # inside an event callback. |
1049 | # inside an event callback. |
530 | our $unblock_scheduler = async { |
1050 | our $unblock_scheduler = new Coro sub { |
531 | while () { |
1051 | while () { |
532 | while (my $cb = pop @unblock_queue) { |
1052 | while (my $cb = pop @unblock_queue) { |
533 | # this is an inlined copy of async_pool |
1053 | &async_pool (@$cb); |
534 | my $coro = (pop @pool or new Coro \&pool_handler); |
|
|
535 | |
1054 | |
536 | $coro->{_invoke} = $cb; |
|
|
537 | $coro->ready; |
|
|
538 | cede; # for short-lived callbacks, this reduces pressure on the coro pool |
1055 | # for short-lived callbacks, this reduces pressure on the coro pool |
|
|
1056 | # as the chance is very high that the async_poll coro will be back |
|
|
1057 | # in the idle state when cede returns |
|
|
1058 | cede; |
539 | } |
1059 | } |
540 | schedule; # sleep well |
1060 | schedule; # sleep well |
541 | } |
1061 | } |
542 | }; |
1062 | }; |
|
|
1063 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
543 | |
1064 | |
544 | sub unblock_sub(&) { |
1065 | sub unblock_sub(&) { |
545 | my $cb = shift; |
1066 | my $cb = shift; |
546 | |
1067 | |
547 | sub { |
1068 | sub { |
548 | unshift @unblock_queue, [$cb, @_]; |
1069 | unshift @unblock_queue, [$cb, @_]; |
549 | $unblock_scheduler->ready; |
1070 | $unblock_scheduler->ready; |
550 | } |
1071 | } |
551 | } |
1072 | } |
552 | |
1073 | |
|
|
1074 | =item $cb = rouse_cb |
|
|
1075 | |
|
|
1076 | Create and return a "rouse callback". That's a code reference that, |
|
|
1077 | when called, will remember a copy of its arguments and notify the owner |
|
|
1078 | coro of the callback. |
|
|
1079 | |
|
|
1080 | See the next function. |
|
|
1081 | |
|
|
1082 | =item @args = rouse_wait [$cb] |
|
|
1083 | |
|
|
1084 | Wait for the specified rouse callback (or the last one that was created in |
|
|
1085 | this coro). |
|
|
1086 | |
|
|
1087 | As soon as the callback is invoked (or when the callback was invoked |
|
|
1088 | before C<rouse_wait>), it will return the arguments originally passed to |
|
|
1089 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
1090 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
1091 | statement at the end. |
|
|
1092 | |
|
|
1093 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
|
|
1094 | |
553 | =back |
1095 | =back |
554 | |
1096 | |
555 | =cut |
1097 | =cut |
556 | |
1098 | |
|
|
1099 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1100 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1101 | |
|
|
1102 | *{"Coro::$module\::new"} = sub { |
|
|
1103 | require "Coro/$module.pm"; |
|
|
1104 | |
|
|
1105 | # some modules have their new predefined in State.xs, some don't |
|
|
1106 | *{"Coro::$module\::new"} = $old |
|
|
1107 | if $old; |
|
|
1108 | |
|
|
1109 | goto &{"Coro::$module\::new"}; |
|
|
1110 | }; |
|
|
1111 | } |
|
|
1112 | |
557 | 1; |
1113 | 1; |
558 | |
1114 | |
|
|
1115 | =head1 HOW TO WAIT FOR A CALLBACK |
|
|
1116 | |
|
|
1117 | It is very common for a coro to wait for some callback to be |
|
|
1118 | called. This occurs naturally when you use coro in an otherwise |
|
|
1119 | event-based program, or when you use event-based libraries. |
|
|
1120 | |
|
|
1121 | These typically register a callback for some event, and call that callback |
|
|
1122 | when the event occured. In a coro, however, you typically want to |
|
|
1123 | just wait for the event, simplyifying things. |
|
|
1124 | |
|
|
1125 | For example C<< AnyEvent->child >> registers a callback to be called when |
|
|
1126 | a specific child has exited: |
|
|
1127 | |
|
|
1128 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
1129 | |
|
|
1130 | But from within a coro, you often just want to write this: |
|
|
1131 | |
|
|
1132 | my $status = wait_for_child $pid; |
|
|
1133 | |
|
|
1134 | Coro offers two functions specifically designed to make this easy, |
|
|
1135 | C<rouse_cb> and C<rouse_wait>. |
|
|
1136 | |
|
|
1137 | The first function, C<rouse_cb>, generates and returns a callback that, |
|
|
1138 | when invoked, will save its arguments and notify the coro that |
|
|
1139 | created the callback. |
|
|
1140 | |
|
|
1141 | The second function, C<rouse_wait>, waits for the callback to be called |
|
|
1142 | (by calling C<schedule> to go to sleep) and returns the arguments |
|
|
1143 | originally passed to the callback. |
|
|
1144 | |
|
|
1145 | Using these functions, it becomes easy to write the C<wait_for_child> |
|
|
1146 | function mentioned above: |
|
|
1147 | |
|
|
1148 | sub wait_for_child($) { |
|
|
1149 | my ($pid) = @_; |
|
|
1150 | |
|
|
1151 | my $watcher = AnyEvent->child (pid => $pid, cb => rouse_cb); |
|
|
1152 | |
|
|
1153 | my ($rpid, $rstatus) = rouse_wait; |
|
|
1154 | $rstatus |
|
|
1155 | } |
|
|
1156 | |
|
|
1157 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
|
|
1158 | you can roll your own, using C<schedule> and C<ready>: |
|
|
1159 | |
|
|
1160 | sub wait_for_child($) { |
|
|
1161 | my ($pid) = @_; |
|
|
1162 | |
|
|
1163 | # store the current coro in $current, |
|
|
1164 | # and provide result variables for the closure passed to ->child |
|
|
1165 | my $current = $Coro::current; |
|
|
1166 | my ($done, $rstatus); |
|
|
1167 | |
|
|
1168 | # pass a closure to ->child |
|
|
1169 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
1170 | $rstatus = $_[1]; # remember rstatus |
|
|
1171 | $done = 1; # mark $rstatus as valid |
|
|
1172 | $current->ready; # wake up the waiting thread |
|
|
1173 | }); |
|
|
1174 | |
|
|
1175 | # wait until the closure has been called |
|
|
1176 | schedule while !$done; |
|
|
1177 | |
|
|
1178 | $rstatus |
|
|
1179 | } |
|
|
1180 | |
|
|
1181 | |
559 | =head1 BUGS/LIMITATIONS |
1182 | =head1 BUGS/LIMITATIONS |
560 | |
1183 | |
561 | - you must make very sure that no coro is still active on global |
1184 | =over 4 |
562 | destruction. very bad things might happen otherwise (usually segfaults). |
|
|
563 | |
1185 | |
|
|
1186 | =item fork with pthread backend |
|
|
1187 | |
|
|
1188 | When Coro is compiled using the pthread backend (which isn't recommended |
|
|
1189 | but required on many BSDs as their libcs are completely broken), then |
|
|
1190 | coro will not survive a fork. There is no known workaround except to |
|
|
1191 | fix your libc and use a saner backend. |
|
|
1192 | |
|
|
1193 | =item perl process emulation ("threads") |
|
|
1194 | |
564 | - this module is not thread-safe. You should only ever use this module |
1195 | This module is not perl-pseudo-thread-safe. You should only ever use this |
565 | from the same thread (this requirement might be losened in the future |
1196 | module from the first thread (this requirement might be removed in the |
566 | to allow per-thread schedulers, but Coro::State does not yet allow |
1197 | future to allow per-thread schedulers, but Coro::State does not yet allow |
567 | this). |
1198 | this). I recommend disabling thread support and using processes, as having |
|
|
1199 | the windows process emulation enabled under unix roughly halves perl |
|
|
1200 | performance, even when not used. |
|
|
1201 | |
|
|
1202 | Attempts to use threads created in another emulated process will crash |
|
|
1203 | ("cleanly", with a null pointer exception). |
|
|
1204 | |
|
|
1205 | =item coro switching is not signal safe |
|
|
1206 | |
|
|
1207 | You must not switch to another coro from within a signal handler (only |
|
|
1208 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1209 | you are sure you are not interrupting a Coro function. |
|
|
1210 | |
|
|
1211 | That means you I<MUST NOT> call any function that might "block" the |
|
|
1212 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
|
|
1213 | anything that calls those. Everything else, including calling C<ready>, |
|
|
1214 | works. |
|
|
1215 | |
|
|
1216 | =back |
|
|
1217 | |
|
|
1218 | |
|
|
1219 | =head1 WINDOWS PROCESS EMULATION |
|
|
1220 | |
|
|
1221 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1222 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1223 | while in the same mail making rather confused statements about perl |
|
|
1224 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1225 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1226 | it is probably not obvious to everybody). |
|
|
1227 | |
|
|
1228 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1229 | scripting languages given on the perl workshop 2009: |
|
|
1230 | |
|
|
1231 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1232 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1233 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1234 | |
|
|
1235 | It does that by using threads instead of OS processes. The difference |
|
|
1236 | between processes and threads is that threads share memory (and other |
|
|
1237 | state, such as files) between threads within a single process, while |
|
|
1238 | processes do not share anything (at least not semantically). That |
|
|
1239 | means that modifications done by one thread are seen by others, while |
|
|
1240 | modifications by one process are not seen by other processes. |
|
|
1241 | |
|
|
1242 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1243 | process, all state is copied (memory is copied physically, files and code |
|
|
1244 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1245 | the same behaviour can be achieved by using operating system processes, |
|
|
1246 | except that UNIX typically uses hardware built into the system to do this |
|
|
1247 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1248 | software (rather efficiently, but of course it is still much slower than |
|
|
1249 | dedicated hardware). |
|
|
1250 | |
|
|
1251 | As mentioned before, loading code, modifying code, modifying data |
|
|
1252 | structures and so on is only visible in the ithreads process doing the |
|
|
1253 | modification, not in other ithread processes within the same OS process. |
|
|
1254 | |
|
|
1255 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1256 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1257 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1258 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1259 | faster). |
|
|
1260 | |
|
|
1261 | Sharing data is in the i-threads model is done by transfering data |
|
|
1262 | structures between threads using copying semantics, which is very slow - |
|
|
1263 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1264 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1265 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1266 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1267 | real threads, refer to my talk for details). |
|
|
1268 | |
|
|
1269 | As summary, i-threads *use* threads to implement processes, while |
|
|
1270 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1271 | processes. I-threads slow down every perl program when enabled, and |
|
|
1272 | outside of windows, serve no (or little) practical purpose, but |
|
|
1273 | disadvantages every single-threaded Perl program. |
|
|
1274 | |
|
|
1275 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1276 | misleading as it implies that it implements some kind of thread model for |
|
|
1277 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1278 | actual use and behaviour of it much better. |
568 | |
1279 | |
569 | =head1 SEE ALSO |
1280 | =head1 SEE ALSO |
570 | |
1281 | |
|
|
1282 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
|
|
1283 | |
|
|
1284 | Debugging: L<Coro::Debug>. |
|
|
1285 | |
571 | Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
1286 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
572 | |
1287 | |
573 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
1288 | Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
1289 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
574 | |
1290 | |
575 | Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
1291 | I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
576 | |
1292 | |
577 | Embedding: L<Coro:MakeMaker> |
1293 | Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
1294 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
1295 | L<Coro::Select>. |
|
|
1296 | |
|
|
1297 | XS API: L<Coro::MakeMaker>. |
|
|
1298 | |
|
|
1299 | Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
578 | |
1300 | |
579 | =head1 AUTHOR |
1301 | =head1 AUTHOR |
580 | |
1302 | |
581 | Marc Lehmann <schmorp@schmorp.de> |
1303 | Marc Lehmann <schmorp@schmorp.de> |
582 | http://home.schmorp.de/ |
1304 | http://home.schmorp.de/ |