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 |
11 | print "2\n"; |
11 | print "2\n"; |
12 | cede; # yield back to main |
12 | cede; # yield back to main |
13 | print "4\n"; |
13 | print "4\n"; |
14 | }; |
14 | }; |
15 | print "1\n"; |
15 | print "1\n"; |
16 | cede; # yield to coroutine |
16 | cede; # yield to coro |
17 | print "3\n"; |
17 | print "3\n"; |
18 | cede; # and again |
18 | cede; # and again |
19 | |
19 | |
20 | # use locking |
20 | # use locking |
21 | my $lock = new Coro::Semaphore; |
21 | my $lock = new Coro::Semaphore; |
22 | my $locked; |
22 | my $locked; |
23 | |
23 | |
24 | $lock->down; |
24 | $lock->down; |
25 | $locked = 1; |
25 | $locked = 1; |
26 | $lock->up; |
26 | $lock->up; |
27 | |
27 | |
28 | =head1 DESCRIPTION |
28 | =head1 DESCRIPTION |
29 | |
29 | |
30 | This module collection manages coroutines. Coroutines are similar |
30 | For a tutorial-style introduction, please read the L<Coro::Intro> |
31 | to threads but don't run in parallel at the same time even on SMP |
31 | manpage. This manpage mainly contains reference information. |
32 | machines. The specific flavor of coroutine used in this module also |
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33 | guarantees you that it will not switch between coroutines unless |
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34 | necessary, at easily-identified points in your program, so locking and |
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35 | parallel access are rarely an issue, making coroutine programming much |
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36 | safer than threads programming. |
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37 | |
32 | |
38 | (Perl, however, does not natively support real threads but instead does a |
33 | This module collection manages continuations in general, most often in |
39 | very slow and memory-intensive emulation of processes using threads. This |
34 | the form of cooperative threads (also called coros, or simply "coro" |
40 | 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. |
41 | |
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 | |
42 | In this module, coroutines are defined as "callchain + lexical variables + |
60 | In this module, a thread is defined as "callchain + lexical variables + |
43 | @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, |
61 | some package variables + C stack), that is, a thread has its own callchain, |
44 | 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 |
45 | variables (see L<Coro::State> for more configuration). |
63 | variables (see L<Coro::State> for more configuration and background info). |
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64 | |
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65 | See also the C<SEE ALSO> section at the end of this document - the Coro |
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66 | module family is quite large. |
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67 | |
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68 | =head1 CORO THREAD LIFE CYCLE |
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69 | |
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70 | During the long and exciting (or not) life of a coro thread, it goes |
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71 | through a number of states: |
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72 | |
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73 | =over 4 |
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74 | |
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75 | =item 1. Creation |
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76 | |
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77 | The first thing in the life of a coro thread is it's creation - |
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78 | obviously. The typical way to create a thread is to call the C<async |
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79 | BLOCK> function: |
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80 | |
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81 | async { |
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82 | # thread code goes here |
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83 | }; |
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84 | |
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85 | You can also pass arguments, which are put in C<@_>: |
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86 | |
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87 | async { |
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88 | print $_[1]; # prints 2 |
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89 | } 1, 2, 3; |
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90 | |
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91 | This creates a new coro thread and puts it into the ready queue, meaning |
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92 | it will run as soon as the CPU is free for it. |
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93 | |
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94 | C<async> will return a Coro object - you can store this for future |
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95 | reference or ignore it - a thread that is running, ready to run or waiting |
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96 | for some event is alive on it's own. |
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97 | |
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98 | Another way to create a thread is to call the C<new> constructor with a |
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99 | code-reference: |
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100 | |
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101 | new Coro sub { |
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102 | # thread code goes here |
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103 | }, @optional_arguments; |
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104 | |
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105 | This is quite similar to calling C<async>, but the important difference is |
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106 | that the new thread is not put into the ready queue, so the thread will |
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107 | not run until somebody puts it there. C<async> is, therefore, identical to |
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108 | this sequence: |
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109 | |
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110 | my $coro = new Coro sub { |
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111 | # thread code goes here |
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112 | }; |
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113 | $coro->ready; |
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114 | return $coro; |
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115 | |
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116 | =item 2. Startup |
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117 | |
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118 | When a new coro thread is created, only a copy of the code reference |
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119 | and the arguments are stored, no extra memory for stacks and so on is |
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120 | allocated, keeping the coro thread in a low-memory state. |
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121 | |
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122 | Only when it actually starts executing will all the resources be finally |
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123 | allocated. |
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124 | |
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125 | The optional arguments specified at coro creation are available in C<@_>, |
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126 | similar to function calls. |
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127 | |
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128 | =item 3. Running / Blocking |
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129 | |
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130 | A lot can happen after the coro thread has started running. Quite usually, |
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131 | it will not run to the end in one go (because you could use a function |
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132 | instead), but it will give up the CPU regularly because it waits for |
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133 | external events. |
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134 | |
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135 | As long as a coro thread runs, its Coro object is available in the global |
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136 | variable C<$Coro::current>. |
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137 | |
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138 | The low-level way to give up the CPU is to call the scheduler, which |
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139 | selects a new coro thread to run: |
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140 | |
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141 | Coro::schedule; |
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142 | |
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143 | Since running threads are not in the ready queue, calling the scheduler |
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144 | without doing anything else will block the coro thread forever - you need |
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145 | to arrange either for the coro to put woken up (readied) by some other |
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146 | event or some other thread, or you can put it into the ready queue before |
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147 | scheduling: |
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148 | |
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149 | # this is exactly what Coro::cede does |
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150 | $Coro::current->ready; |
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151 | Coro::schedule; |
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152 | |
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153 | All the higher-level synchronisation methods (Coro::Semaphore, |
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154 | Coro::rouse_*...) are actually implemented via C<< ->ready >> and C<< |
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155 | Coro::schedule >>. |
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156 | |
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157 | While the coro thread is running it also might get assigned a C-level |
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158 | thread, or the C-level thread might be unassigned from it, as the Coro |
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159 | runtime wishes. A C-level thread needs to be assigned when your perl |
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160 | thread calls into some C-level function and that function in turn calls |
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161 | perl and perl then wants to switch coroutines. This happens most often |
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162 | when you run an event loop and block in the callback, or when perl |
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163 | itself calls some function such as C<AUTOLOAD> or methods via the C<tie> |
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164 | mechanism. |
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165 | |
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166 | =item 4. Termination |
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167 | |
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168 | Many threads actually terminate after some time. There are a number of |
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169 | ways to terminate a coro thread, the simplest is returning from the |
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170 | top-level code reference: |
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171 | |
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172 | async { |
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173 | # after returning from here, the coro thread is terminated |
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174 | }; |
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175 | |
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176 | async { |
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177 | return if 0.5 < rand; # terminate a little earlier, maybe |
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178 | print "got a chance to print this\n"; |
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179 | # or here |
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180 | }; |
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181 | |
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182 | Any values returned from the coroutine can be recovered using C<< ->join |
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183 | >>: |
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184 | |
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185 | my $coro = async { |
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186 | "hello, world\n" # return a string |
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187 | }; |
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188 | |
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189 | my $hello_world = $coro->join; |
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190 | |
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191 | print $hello_world; |
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192 | |
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193 | Another way to terminate is to call C<< Coro::terminate >>, which at any |
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194 | subroutine call nesting level: |
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195 | |
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196 | async { |
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197 | Coro::terminate "return value 1", "return value 2"; |
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198 | }; |
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199 | |
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200 | And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the |
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201 | coro thread from another thread: |
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202 | |
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203 | my $coro = async { |
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204 | exit 1; |
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205 | }; |
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206 | |
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207 | $coro->cancel; # also accepts values for ->join to retrieve |
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208 | |
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209 | Cancellation I<can> be dangerous - it's a bit like calling C<exit> without |
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210 | actually exiting, and might leave C libraries and XS modules in a weird |
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211 | state. Unlike other thread implementations, however, Coro is exceptionally |
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212 | safe with regards to cancellation, as perl will always be in a consistent |
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213 | state, and for those cases where you want to do truly marvellous things |
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214 | with your coro while it is being cancelled - that is, make sure all |
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215 | cleanup code is executed from the thread being cancelled - there is even a |
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216 | C<< ->safe_cancel >> method. |
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217 | |
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218 | So, cancelling a thread that runs in an XS event loop might not be the |
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219 | best idea, but any other combination that deals with perl only (cancelling |
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220 | when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is |
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221 | safe. |
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222 | |
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223 | Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed |
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224 | automatically - just like other objects in Perl. This is not such a common |
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225 | case, however - a running thread is referencedy b C<$Coro::current>, a |
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226 | thread ready to run is referenced by the ready queue, a thread waiting |
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227 | on a lock or semaphore is referenced by being in some wait list and so |
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228 | on. But a thread that isn't in any of those queues gets cancelled: |
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229 | |
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230 | async { |
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231 | schedule; # cede to other coros, don't go into the ready queue |
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232 | }; |
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233 | |
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234 | cede; |
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235 | # now the async above is destroyed, as it is not referenced by anything. |
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236 | |
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237 | =item 5. Cleanup |
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238 | |
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239 | Threads will allocate various resources. Most but not all will be returned |
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240 | when a thread terminates, during clean-up. |
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241 | |
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242 | Cleanup is quite similar to throwing an uncaught exception: perl will |
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243 | work it's way up through all subroutine calls and blocks. On it's way, it |
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244 | will release all C<my> variables, undo all C<local>'s and free any other |
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245 | resources truly local to the thread. |
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246 | |
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247 | So, a common way to free resources is to keep them referenced only by my |
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248 | variables: |
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249 | |
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250 | async { |
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251 | my $big_cache = new Cache ...; |
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252 | }; |
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253 | |
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254 | If there are no other references, then the C<$big_cache> object will be |
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255 | freed when the thread terminates, regardless of how it does so. |
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256 | |
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257 | What it does C<NOT> do is unlock any Coro::Semaphores or similar |
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258 | resources, but that's where the C<guard> methods come in handy: |
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259 | |
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260 | my $sem = new Coro::Semaphore; |
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261 | |
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262 | async { |
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263 | my $lock_guard = $sem->guard; |
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264 | # if we reutrn, or die or get cancelled, here, |
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265 | # then the semaphore will be "up"ed. |
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266 | }; |
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267 | |
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268 | The C<Guard::guard> function comes in handy for any custom cleanup you |
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269 | might want to do (but you cannot switch to other coroutines form those |
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270 | code blocks): |
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271 | |
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272 | async { |
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273 | my $window = new Gtk2::Window "toplevel"; |
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274 | # The window will not be cleaned up automatically, even when $window |
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275 | # gets freed, so use a guard to ensure it's destruction |
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276 | # in case of an error: |
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277 | my $window_guard = Guard::guard { $window->destroy }; |
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278 | |
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279 | # we are safe here |
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280 | }; |
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281 | |
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282 | Last not least, C<local> can often be handy, too, e.g. when temporarily |
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283 | replacing the coro thread description: |
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284 | |
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285 | sub myfunction { |
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286 | local $Coro::current->{desc} = "inside myfunction(@_)"; |
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287 | |
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288 | # if we return or die here, the description will be restored |
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289 | } |
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290 | |
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291 | =item 6. Viva La Zombie Muerte |
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292 | |
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293 | Even after a thread has terminated and cleaned up its resources, the Coro |
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294 | object still is there and stores the return values of the thread. |
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295 | |
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296 | The means the Coro object gets freed automatically when the thread has |
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297 | terminated and cleaned up and there arenot other references. |
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298 | |
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299 | If there are, the Coro object will stay around, and you can call C<< |
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300 | ->join >> as many times as you wish to retrieve the result values: |
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301 | |
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302 | async { |
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303 | print "hi\n"; |
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304 | 1 |
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305 | }; |
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306 | |
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307 | # run the async above, and free everything before returning |
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308 | # from Coro::cede: |
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309 | Coro::cede; |
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310 | |
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311 | { |
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312 | my $coro = async { |
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313 | print "hi\n"; |
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314 | 1 |
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315 | }; |
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316 | |
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317 | # run the async above, and clean up, but do not free the coro |
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318 | # object: |
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319 | Coro::cede; |
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320 | |
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321 | # optionally retrieve the result values |
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322 | my @results = $coro->join; |
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323 | |
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324 | # now $coro goes out of scope, and presumably gets freed |
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325 | }; |
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326 | |
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327 | =back |
46 | |
328 | |
47 | =cut |
329 | =cut |
48 | |
330 | |
49 | package Coro; |
331 | package Coro; |
50 | |
332 | |
51 | use strict; |
333 | use common::sense; |
52 | no warnings "uninitialized"; |
334 | |
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335 | use Carp (); |
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336 | |
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337 | use Guard (); |
53 | |
338 | |
54 | use Coro::State; |
339 | use Coro::State; |
55 | |
340 | |
56 | use base qw(Coro::State Exporter); |
341 | use base qw(Coro::State Exporter); |
57 | |
342 | |
58 | our $idle; # idle handler |
343 | our $idle; # idle handler |
59 | our $main; # main coroutine |
344 | our $main; # main coro |
60 | our $current; # current coroutine |
345 | our $current; # current coro |
61 | |
346 | |
62 | our $VERSION = '4.4'; |
347 | our $VERSION = 5.372; |
63 | |
348 | |
64 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
349 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
65 | our %EXPORT_TAGS = ( |
350 | our %EXPORT_TAGS = ( |
66 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
351 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
67 | ); |
352 | ); |
68 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
353 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
69 | |
354 | |
70 | { |
355 | =head1 GLOBAL VARIABLES |
71 | my @async; |
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72 | my $init; |
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73 | |
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74 | # this way of handling attributes simply is NOT scalable ;() |
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75 | sub import { |
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76 | no strict 'refs'; |
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77 | |
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78 | Coro->export_to_level (1, @_); |
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79 | |
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80 | my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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81 | *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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82 | my ($package, $ref) = (shift, shift); |
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83 | my @attrs; |
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84 | for (@_) { |
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85 | if ($_ eq "Coro") { |
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86 | push @async, $ref; |
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87 | unless ($init++) { |
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88 | eval q{ |
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89 | sub INIT { |
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90 | &async(pop @async) while @async; |
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91 | } |
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92 | }; |
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93 | } |
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94 | } else { |
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95 | push @attrs, $_; |
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96 | } |
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97 | } |
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98 | return $old ? $old->($package, $ref, @attrs) : @attrs; |
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99 | }; |
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100 | } |
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101 | |
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102 | } |
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103 | |
356 | |
104 | =over 4 |
357 | =over 4 |
105 | |
358 | |
106 | =item $main |
359 | =item $Coro::main |
107 | |
360 | |
108 | This coroutine represents the main program. |
361 | This variable stores the Coro object that represents the main |
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362 | program. While you cna C<ready> it and do most other things you can do to |
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363 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
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364 | whether you are running in the main program or not. |
109 | |
365 | |
110 | =cut |
366 | =cut |
111 | |
367 | |
112 | $main = new Coro; |
368 | # $main is now being initialised by Coro::State |
113 | |
369 | |
114 | =item $current (or as function: current) |
370 | =item $Coro::current |
115 | |
371 | |
116 | The current coroutine (the last coroutine switched to). The initial value |
372 | The Coro object representing the current coro (the last |
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373 | coro that the Coro scheduler switched to). The initial value is |
117 | is C<$main> (of course). |
374 | C<$Coro::main> (of course). |
118 | |
375 | |
119 | This variable is B<strictly> I<read-only>. It is provided for performance |
376 | This variable is B<strictly> I<read-only>. You can take copies of the |
120 | reasons. If performance is not essential you are encouraged to use the |
377 | value stored in it and use it as any other Coro object, but you must |
121 | C<Coro::current> function instead. |
378 | not otherwise modify the variable itself. |
122 | |
379 | |
123 | =cut |
380 | =cut |
124 | |
381 | |
125 | $main->{desc} = "[main::]"; |
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126 | |
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127 | # maybe some other module used Coro::Specific before... |
|
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128 | $main->{_specific} = $current->{_specific} |
|
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129 | if $current; |
|
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130 | |
|
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131 | _set_current $main; |
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132 | |
|
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133 | sub current() { $current } |
382 | sub current() { $current } # [DEPRECATED] |
134 | |
383 | |
135 | =item $idle |
384 | =item $Coro::idle |
136 | |
385 | |
137 | A callback that is called whenever the scheduler finds no ready coroutines |
386 | This variable is mainly useful to integrate Coro into event loops. It is |
|
|
387 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
|
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388 | pretty low-level functionality. |
|
|
389 | |
|
|
390 | This variable stores a Coro object that is put into the ready queue when |
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391 | there are no other ready threads (without invoking any ready hooks). |
|
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392 | |
138 | to run. The default implementation prints "FATAL: deadlock detected" and |
393 | The default implementation dies with "FATAL: deadlock detected.", followed |
139 | exits, because the program has no other way to continue. |
394 | by a thread listing, because the program has no other way to continue. |
140 | |
395 | |
141 | This hook is overwritten by modules such as C<Coro::Timer> and |
396 | This hook is overwritten by modules such as C<Coro::EV> and |
142 | C<Coro::Event> to wait on an external event that hopefully wake up a |
397 | C<Coro::AnyEvent> to wait on an external event that hopefully wakes up a |
143 | coroutine so the scheduler can run it. |
398 | coro so the scheduler can run it. |
144 | |
399 | |
145 | Please note that if your callback recursively invokes perl (e.g. for event |
400 | See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
146 | handlers), then it must be prepared to be called recursively itself. |
|
|
147 | |
401 | |
148 | =cut |
402 | =cut |
149 | |
403 | |
150 | $idle = sub { |
404 | # ||= because other modules could have provided their own by now |
151 | require Carp; |
405 | $idle ||= new Coro sub { |
152 | Carp::croak ("FATAL: deadlock detected"); |
406 | require Coro::Debug; |
|
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407 | die "FATAL: deadlock detected.\n" |
|
|
408 | . Coro::Debug::ps_listing (); |
153 | }; |
409 | }; |
154 | |
410 | |
155 | sub _cancel { |
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156 | my ($self) = @_; |
|
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157 | |
|
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158 | # free coroutine data and mark as destructed |
|
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159 | $self->_destroy |
|
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160 | or return; |
|
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161 | |
|
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162 | # call all destruction callbacks |
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163 | $_->(@{$self->{_status}}) |
|
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164 | for @{(delete $self->{_on_destroy}) || []}; |
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165 | } |
|
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166 | |
|
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167 | # this coroutine is necessary because a coroutine |
411 | # this coro is necessary because a coro |
168 | # cannot destroy itself. |
412 | # cannot destroy itself. |
169 | my @destroy; |
413 | our @destroy; |
170 | my $manager; |
414 | our $manager; |
171 | |
415 | |
172 | $manager = new Coro sub { |
416 | $manager = new Coro sub { |
173 | while () { |
417 | while () { |
174 | (shift @destroy)->_cancel |
418 | _destroy shift @destroy |
175 | while @destroy; |
419 | while @destroy; |
176 | |
420 | |
177 | &schedule; |
421 | &schedule; |
178 | } |
422 | } |
179 | }; |
423 | }; |
180 | $manager->desc ("[coro manager]"); |
424 | $manager->{desc} = "[coro manager]"; |
181 | $manager->prio (PRIO_MAX); |
425 | $manager->prio (PRIO_MAX); |
182 | |
426 | |
183 | # static methods. not really. |
|
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184 | |
|
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185 | =back |
427 | =back |
186 | |
428 | |
187 | =head2 STATIC METHODS |
429 | =head1 SIMPLE CORO CREATION |
188 | |
|
|
189 | Static methods are actually functions that operate on the current coroutine only. |
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190 | |
430 | |
191 | =over 4 |
431 | =over 4 |
192 | |
432 | |
193 | =item async { ... } [@args...] |
433 | =item async { ... } [@args...] |
194 | |
434 | |
195 | Create a new asynchronous coroutine and return it's coroutine object |
435 | Create a new coro and return its Coro object (usually |
196 | (usually unused). When the sub returns the new coroutine is automatically |
436 | unused). The coro will be put into the ready queue, so |
|
|
437 | it will start running automatically on the next scheduler run. |
|
|
438 | |
|
|
439 | The first argument is a codeblock/closure that should be executed in the |
|
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440 | coro. When it returns argument returns the coro is automatically |
197 | terminated. |
441 | terminated. |
198 | |
442 | |
|
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443 | The remaining arguments are passed as arguments to the closure. |
|
|
444 | |
199 | See the C<Coro::State::new> constructor for info about the coroutine |
445 | See the C<Coro::State::new> constructor for info about the coro |
200 | environment in which coroutines run. |
446 | environment in which coro are executed. |
201 | |
447 | |
202 | Calling C<exit> in a coroutine will do the same as calling exit outside |
448 | Calling C<exit> in a coro will do the same as calling exit outside |
203 | the coroutine. Likewise, when the coroutine dies, the program will exit, |
449 | the coro. Likewise, when the coro dies, the program will exit, |
204 | just as it would in the main program. |
450 | just as it would in the main program. |
205 | |
451 | |
|
|
452 | If you do not want that, you can provide a default C<die> handler, or |
|
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453 | simply avoid dieing (by use of C<eval>). |
|
|
454 | |
206 | # create a new coroutine that just prints its arguments |
455 | Example: Create a new coro that just prints its arguments. |
|
|
456 | |
207 | async { |
457 | async { |
208 | print "@_\n"; |
458 | print "@_\n"; |
209 | } 1,2,3,4; |
459 | } 1,2,3,4; |
210 | |
460 | |
211 | =cut |
|
|
212 | |
|
|
213 | sub async(&@) { |
|
|
214 | my $coro = new Coro @_; |
|
|
215 | $coro->ready; |
|
|
216 | $coro |
|
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217 | } |
|
|
218 | |
|
|
219 | =item async_pool { ... } [@args...] |
461 | =item async_pool { ... } [@args...] |
220 | |
462 | |
221 | Similar to C<async>, but uses a coroutine pool, so you should not call |
463 | Similar to C<async>, but uses a coro pool, so you should not call |
222 | terminate or join (although you are allowed to), and you get a coroutine |
464 | terminate or join on it (although you are allowed to), and you get a |
223 | that might have executed other code already (which can be good or bad :). |
465 | coro that might have executed other code already (which can be good |
|
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466 | or bad :). |
224 | |
467 | |
|
|
468 | On the plus side, this function is about twice as fast as creating (and |
|
|
469 | destroying) a completely new coro, so if you need a lot of generic |
|
|
470 | coros in quick successsion, use C<async_pool>, not C<async>. |
|
|
471 | |
225 | Also, the block is executed in an C<eval> context and a warning will be |
472 | The code block is executed in an C<eval> context and a warning will be |
226 | issued in case of an exception instead of terminating the program, as |
473 | issued in case of an exception instead of terminating the program, as |
227 | C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
474 | C<async> does. As the coro is being reused, stuff like C<on_destroy> |
228 | will not work in the expected way, unless you call terminate or cancel, |
475 | will not work in the expected way, unless you call terminate or cancel, |
229 | which somehow defeats the purpose of pooling. |
476 | which somehow defeats the purpose of pooling (but is fine in the |
|
|
477 | exceptional case). |
230 | |
478 | |
231 | The priority will be reset to C<0> after each job, tracing will be |
479 | The priority will be reset to C<0> after each run, tracing will be |
232 | disabled, the description will be reset and the default output filehandle |
480 | disabled, the description will be reset and the default output filehandle |
233 | gets restored, so you can change alkl these. Otherwise the coroutine will |
481 | gets restored, so you can change all these. Otherwise the coro will |
234 | be re-used "as-is": most notably if you change other per-coroutine global |
482 | be re-used "as-is": most notably if you change other per-coro global |
235 | stuff such as C<$/> you need to revert that change, which is most simply |
483 | stuff such as C<$/> you I<must needs> revert that change, which is most |
236 | done by using local as in C< local $/ >. |
484 | simply done by using local as in: C<< local $/ >>. |
237 | |
485 | |
238 | The pool size is limited to 8 idle coroutines (this can be adjusted by |
486 | The idle pool size is limited to C<8> idle coros (this can be |
239 | changing $Coro::POOL_SIZE), and there can be as many non-idle coros as |
487 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
240 | required. |
488 | coros as required. |
241 | |
489 | |
242 | If you are concerned about pooled coroutines growing a lot because a |
490 | If you are concerned about pooled coros growing a lot because a |
243 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
491 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
244 | { terminate }> once per second or so to slowly replenish the pool. In |
492 | { terminate }> once per second or so to slowly replenish the pool. In |
245 | addition to that, when the stacks used by a handler grows larger than 16kb |
493 | addition to that, when the stacks used by a handler grows larger than 32kb |
246 | (adjustable with $Coro::POOL_RSS) it will also exit. |
494 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
247 | |
495 | |
248 | =cut |
496 | =cut |
249 | |
497 | |
250 | our $POOL_SIZE = 8; |
498 | our $POOL_SIZE = 8; |
251 | our $POOL_RSS = 16 * 1024; |
499 | our $POOL_RSS = 32 * 1024; |
252 | our @async_pool; |
500 | our @async_pool; |
253 | |
501 | |
254 | sub pool_handler { |
502 | sub pool_handler { |
255 | my $cb; |
|
|
256 | |
|
|
257 | while () { |
503 | while () { |
258 | eval { |
504 | eval { |
259 | while () { |
505 | &{&_pool_handler} while 1; |
260 | _pool_1 $cb; |
|
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261 | &$cb; |
|
|
262 | _pool_2 $cb; |
|
|
263 | &schedule; |
|
|
264 | } |
|
|
265 | }; |
506 | }; |
266 | |
507 | |
267 | last if $@ eq "\3async_pool terminate\2\n"; |
|
|
268 | warn $@ if $@; |
508 | warn $@ if $@; |
269 | } |
509 | } |
270 | } |
510 | } |
271 | |
511 | |
272 | sub async_pool(&@) { |
512 | =back |
273 | # this is also inlined into the unlock_scheduler |
|
|
274 | my $coro = (pop @async_pool) || new Coro \&pool_handler; |
|
|
275 | |
513 | |
276 | $coro->{_invoke} = [@_]; |
514 | =head1 STATIC METHODS |
277 | $coro->ready; |
|
|
278 | |
515 | |
279 | $coro |
516 | Static methods are actually functions that implicitly operate on the |
280 | } |
517 | current coro. |
|
|
518 | |
|
|
519 | =over 4 |
281 | |
520 | |
282 | =item schedule |
521 | =item schedule |
283 | |
522 | |
284 | Calls the scheduler. Please note that the current coroutine will not be put |
523 | Calls the scheduler. The scheduler will find the next coro that is |
|
|
524 | to be run from the ready queue and switches to it. The next coro |
|
|
525 | to be run is simply the one with the highest priority that is longest |
|
|
526 | in its ready queue. If there is no coro ready, it will call the |
|
|
527 | C<$Coro::idle> hook. |
|
|
528 | |
|
|
529 | Please note that the current coro will I<not> be put into the ready |
285 | into the ready queue, so calling this function usually means you will |
530 | queue, so calling this function usually means you will never be called |
286 | never be called again unless something else (e.g. an event handler) calls |
531 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
287 | ready. |
532 | thus waking you up. |
288 | |
533 | |
289 | The canonical way to wait on external events is this: |
534 | This makes C<schedule> I<the> generic method to use to block the current |
|
|
535 | coro and wait for events: first you remember the current coro in |
|
|
536 | a variable, then arrange for some callback of yours to call C<< ->ready |
|
|
537 | >> on that once some event happens, and last you call C<schedule> to put |
|
|
538 | yourself to sleep. Note that a lot of things can wake your coro up, |
|
|
539 | so you need to check whether the event indeed happened, e.g. by storing the |
|
|
540 | status in a variable. |
290 | |
541 | |
291 | { |
542 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
292 | # remember current coroutine |
|
|
293 | my $current = $Coro::current; |
|
|
294 | |
543 | |
295 | # register a hypothetical event handler |
544 | =item cede |
296 | on_event_invoke sub { |
545 | |
297 | # wake up sleeping coroutine |
546 | "Cede" to other coros. This function puts the current coro into |
298 | $current->ready; |
547 | the ready queue and calls C<schedule>, which has the effect of giving |
299 | undef $current; |
548 | up the current "timeslice" to other coros of the same or higher |
|
|
549 | priority. Once your coro gets its turn again it will automatically be |
|
|
550 | resumed. |
|
|
551 | |
|
|
552 | This function is often called C<yield> in other languages. |
|
|
553 | |
|
|
554 | =item Coro::cede_notself |
|
|
555 | |
|
|
556 | Works like cede, but is not exported by default and will cede to I<any> |
|
|
557 | coro, regardless of priority. This is useful sometimes to ensure |
|
|
558 | progress is made. |
|
|
559 | |
|
|
560 | =item terminate [arg...] |
|
|
561 | |
|
|
562 | Terminates the current coro with the given status values (see |
|
|
563 | L<cancel>). The values will not be copied, but referenced directly. |
|
|
564 | |
|
|
565 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
|
|
566 | |
|
|
567 | These function install enter and leave winders in the current scope. The |
|
|
568 | enter block will be executed when on_enter is called and whenever the |
|
|
569 | current coro is re-entered by the scheduler, while the leave block is |
|
|
570 | executed whenever the current coro is blocked by the scheduler, and |
|
|
571 | also when the containing scope is exited (by whatever means, be it exit, |
|
|
572 | die, last etc.). |
|
|
573 | |
|
|
574 | I<Neither invoking the scheduler, nor exceptions, are allowed within those |
|
|
575 | BLOCKs>. That means: do not even think about calling C<die> without an |
|
|
576 | eval, and do not even think of entering the scheduler in any way. |
|
|
577 | |
|
|
578 | Since both BLOCKs are tied to the current scope, they will automatically |
|
|
579 | be removed when the current scope exits. |
|
|
580 | |
|
|
581 | These functions implement the same concept as C<dynamic-wind> in scheme |
|
|
582 | does, and are useful when you want to localise some resource to a specific |
|
|
583 | coro. |
|
|
584 | |
|
|
585 | They slow down thread switching considerably for coros that use them |
|
|
586 | (about 40% for a BLOCK with a single assignment, so thread switching is |
|
|
587 | still reasonably fast if the handlers are fast). |
|
|
588 | |
|
|
589 | These functions are best understood by an example: The following function |
|
|
590 | will change the current timezone to "Antarctica/South_Pole", which |
|
|
591 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
|
|
592 | which remember/change the current timezone and restore the previous |
|
|
593 | value, respectively, the timezone is only changed for the coro that |
|
|
594 | installed those handlers. |
|
|
595 | |
|
|
596 | use POSIX qw(tzset); |
|
|
597 | |
|
|
598 | async { |
|
|
599 | my $old_tz; # store outside TZ value here |
|
|
600 | |
|
|
601 | Coro::on_enter { |
|
|
602 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
603 | |
|
|
604 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
|
605 | tzset; # enable new value |
300 | }; |
606 | }; |
301 | |
607 | |
302 | # call schedule until event occurred. |
608 | Coro::on_leave { |
303 | # in case we are woken up for other reasons |
609 | $ENV{TZ} = $old_tz; |
304 | # (current still defined), loop. |
610 | tzset; # restore old value |
305 | Coro::schedule while $current; |
611 | }; |
|
|
612 | |
|
|
613 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
614 | # without disturbing the TZ of any other coro. |
306 | } |
615 | }; |
307 | |
616 | |
308 | =item cede |
617 | This can be used to localise about any resource (locale, uid, current |
|
|
618 | working directory etc.) to a block, despite the existance of other |
|
|
619 | coros. |
309 | |
620 | |
310 | "Cede" to other coroutines. This function puts the current coroutine into the |
621 | Another interesting example implements time-sliced multitasking using |
311 | ready queue and calls C<schedule>, which has the effect of giving up the |
622 | interval timers (this could obviously be optimised, but does the job): |
312 | current "timeslice" to other coroutines of the same or higher priority. |
|
|
313 | |
623 | |
314 | =item Coro::cede_notself |
624 | # "timeslice" the given block |
|
|
625 | sub timeslice(&) { |
|
|
626 | use Time::HiRes (); |
315 | |
627 | |
316 | Works like cede, but is not exported by default and will cede to any |
628 | Coro::on_enter { |
317 | coroutine, regardless of priority, once. |
629 | # on entering the thread, we set an VTALRM handler to cede |
|
|
630 | $SIG{VTALRM} = sub { cede }; |
|
|
631 | # and then start the interval timer |
|
|
632 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
633 | }; |
|
|
634 | Coro::on_leave { |
|
|
635 | # on leaving the thread, we stop the interval timer again |
|
|
636 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
637 | }; |
318 | |
638 | |
319 | =item terminate [arg...] |
639 | &{+shift}; |
|
|
640 | } |
320 | |
641 | |
321 | Terminates the current coroutine with the given status values (see L<cancel>). |
642 | # use like this: |
|
|
643 | timeslice { |
|
|
644 | # The following is an endless loop that would normally |
|
|
645 | # monopolise the process. Since it runs in a timesliced |
|
|
646 | # environment, it will regularly cede to other threads. |
|
|
647 | while () { } |
|
|
648 | }; |
|
|
649 | |
322 | |
650 | |
323 | =item killall |
651 | =item killall |
324 | |
652 | |
325 | Kills/terminates/cancels all coroutines except the currently running |
653 | Kills/terminates/cancels all coros except the currently running one. |
326 | one. This is useful after a fork, either in the child or the parent, as |
654 | |
327 | usually only one of them should inherit the running coroutines. |
655 | Note that while this will try to free some of the main interpreter |
|
|
656 | resources if the calling coro isn't the main coro, but one |
|
|
657 | cannot free all of them, so if a coro that is not the main coro |
|
|
658 | calls this function, there will be some one-time resource leak. |
328 | |
659 | |
329 | =cut |
660 | =cut |
330 | |
|
|
331 | sub terminate { |
|
|
332 | $current->cancel (@_); |
|
|
333 | } |
|
|
334 | |
661 | |
335 | sub killall { |
662 | sub killall { |
336 | for (Coro::State::list) { |
663 | for (Coro::State::list) { |
337 | $_->cancel |
664 | $_->cancel |
338 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
665 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
339 | } |
666 | } |
340 | } |
667 | } |
341 | |
668 | |
342 | =back |
669 | =back |
343 | |
670 | |
344 | # dynamic methods |
|
|
345 | |
|
|
346 | =head2 COROUTINE METHODS |
671 | =head1 CORO OBJECT METHODS |
347 | |
672 | |
348 | These are the methods you can call on coroutine objects. |
673 | These are the methods you can call on coro objects (or to create |
|
|
674 | them). |
349 | |
675 | |
350 | =over 4 |
676 | =over 4 |
351 | |
677 | |
352 | =item new Coro \&sub [, @args...] |
678 | =item new Coro \&sub [, @args...] |
353 | |
679 | |
354 | Create a new coroutine and return it. When the sub returns the coroutine |
680 | Create a new coro and return it. When the sub returns, the coro |
355 | automatically terminates as if C<terminate> with the returned values were |
681 | automatically terminates as if C<terminate> with the returned values were |
356 | called. To make the coroutine run you must first put it into the ready queue |
682 | called. To make the coro run you must first put it into the ready |
357 | by calling the ready method. |
683 | queue by calling the ready method. |
358 | |
684 | |
359 | See C<async> and C<Coro::State::new> for additional info about the |
685 | See C<async> and C<Coro::State::new> for additional info about the |
360 | coroutine environment. |
686 | coro environment. |
361 | |
687 | |
362 | =cut |
688 | =cut |
363 | |
689 | |
364 | sub _run_coro { |
690 | sub _coro_run { |
365 | terminate &{+shift}; |
691 | terminate &{+shift}; |
366 | } |
692 | } |
367 | |
693 | |
368 | sub new { |
|
|
369 | my $class = shift; |
|
|
370 | |
|
|
371 | $class->SUPER::new (\&_run_coro, @_) |
|
|
372 | } |
|
|
373 | |
|
|
374 | =item $success = $coroutine->ready |
694 | =item $success = $coro->ready |
375 | |
695 | |
376 | Put the given coroutine into the ready queue (according to it's priority) |
696 | Put the given coro into the end of its ready queue (there is one |
377 | and return true. If the coroutine is already in the ready queue, do nothing |
697 | queue for each priority) and return true. If the coro is already in |
378 | and return false. |
698 | the ready queue, do nothing and return false. |
379 | |
699 | |
|
|
700 | This ensures that the scheduler will resume this coro automatically |
|
|
701 | once all the coro of higher priority and all coro of the same |
|
|
702 | priority that were put into the ready queue earlier have been resumed. |
|
|
703 | |
|
|
704 | =item $coro->suspend |
|
|
705 | |
|
|
706 | Suspends the specified coro. A suspended coro works just like any other |
|
|
707 | coro, except that the scheduler will not select a suspended coro for |
|
|
708 | execution. |
|
|
709 | |
|
|
710 | Suspending a coro can be useful when you want to keep the coro from |
|
|
711 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
712 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
713 | |
|
|
714 | A scenario for the former would be to suspend all (other) coros after a |
|
|
715 | fork and keep them alive, so their destructors aren't called, but new |
|
|
716 | coros can be created. |
|
|
717 | |
|
|
718 | =item $coro->resume |
|
|
719 | |
|
|
720 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
721 | the coro was in the ready queue when it was suspended, it might have been |
|
|
722 | unreadied by the scheduler, so an activation might have been lost. |
|
|
723 | |
|
|
724 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
725 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
726 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
727 | that. |
|
|
728 | |
|
|
729 | =item $state->is_new |
|
|
730 | |
|
|
731 | Returns true iff this Coro object is "new", i.e. has never been run |
|
|
732 | yet. Those states basically consist of only the code reference to call and |
|
|
733 | the arguments, but consumes very little other resources. New states will |
|
|
734 | automatically get assigned a perl interpreter when they are transfered to. |
|
|
735 | |
|
|
736 | =item $state->is_zombie |
|
|
737 | |
|
|
738 | Returns true iff the Coro object has been cancelled, i.e. |
|
|
739 | it's resources freed because they were C<cancel>'ed, C<terminate>'d, |
|
|
740 | C<safe_cancel>'ed or simply went out of scope. |
|
|
741 | |
|
|
742 | The name "zombie" stems from UNIX culture, where a process that has |
|
|
743 | exited and only stores and exit status and no other resources is called a |
|
|
744 | "zombie". |
|
|
745 | |
380 | =item $is_ready = $coroutine->is_ready |
746 | =item $is_ready = $coro->is_ready |
381 | |
747 | |
382 | Return wether the coroutine is currently the ready queue or not, |
748 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
|
|
749 | object gets destroyed, it will eventually be scheduled by the scheduler. |
383 | |
750 | |
|
|
751 | =item $is_running = $coro->is_running |
|
|
752 | |
|
|
753 | Returns true iff the Coro object is currently running. Only one Coro object |
|
|
754 | can ever be in the running state (but it currently is possible to have |
|
|
755 | multiple running Coro::States). |
|
|
756 | |
|
|
757 | =item $is_suspended = $coro->is_suspended |
|
|
758 | |
|
|
759 | Returns true iff this Coro object has been suspended. Suspended Coros will |
|
|
760 | not ever be scheduled. |
|
|
761 | |
384 | =item $coroutine->cancel (arg...) |
762 | =item $coro->cancel (arg...) |
385 | |
763 | |
386 | Terminates the given coroutine and makes it return the given arguments as |
764 | Terminates the given Coro thread and makes it return the given arguments as |
387 | status (default: the empty list). Never returns if the coroutine is the |
765 | status (default: an empty list). Never returns if the Coro is the |
388 | current coroutine. |
766 | current Coro. |
389 | |
767 | |
390 | =cut |
768 | This is a rather brutal way to free a coro, with some limitations - if |
|
|
769 | the thread is inside a C callback that doesn't expect to be canceled, |
|
|
770 | bad things can happen, or if the cancelled thread insists on running |
|
|
771 | complicated cleanup handlers that rely on its thread context, things will |
|
|
772 | not work. |
391 | |
773 | |
392 | sub cancel { |
774 | Any cleanup code being run (e.g. from C<guard> blocks) will be run without |
393 | my $self = shift; |
775 | a thread context, and is not allowed to switch to other threads. On the |
394 | $self->{_status} = [@_]; |
776 | plus side, C<< ->cancel >> will always clean up the thread, no matter |
|
|
777 | what. If your cleanup code is complex or you want to avoid cancelling a |
|
|
778 | C-thread that doesn't know how to clean up itself, it can be better to C<< |
|
|
779 | ->throw >> an exception, or use C<< ->safe_cancel >>. |
395 | |
780 | |
396 | if ($current == $self) { |
781 | The arguments to C<< ->cancel >> are not copied, but instead will |
397 | push @destroy, $self; |
782 | be referenced directly (e.g. if you pass C<$var> and after the call |
398 | $manager->ready; |
783 | change that variable, then you might change the return values passed to |
399 | &schedule while 1; |
784 | e.g. C<join>, so don't do that). |
400 | } else { |
785 | |
401 | $self->_cancel; |
786 | The resources of the Coro are usually freed (or destructed) before this |
|
|
787 | call returns, but this can be delayed for an indefinite amount of time, as |
|
|
788 | in some cases the manager thread has to run first to actually destruct the |
|
|
789 | Coro object. |
|
|
790 | |
|
|
791 | =item $coro->safe_cancel ($arg...) |
|
|
792 | |
|
|
793 | Works mostly like C<< ->cancel >>, but is inherently "safer", and |
|
|
794 | consequently, can fail with an exception in cases the thread is not in a |
|
|
795 | cancellable state. |
|
|
796 | |
|
|
797 | This method works a bit like throwing an exception that cannot be caught |
|
|
798 | - specifically, it will clean up the thread from within itself, so |
|
|
799 | all cleanup handlers (e.g. C<guard> blocks) are run with full thread |
|
|
800 | context and can block if they wish. The downside is that there is no |
|
|
801 | guarantee that the thread can be cancelled when you call this method, and |
|
|
802 | therefore, it might fail. It is also considerably slower than C<cancel> or |
|
|
803 | C<terminate>. |
|
|
804 | |
|
|
805 | A thread is in a safe-cancellable state if it either hasn't been run yet, |
|
|
806 | or it has no C context attached and is inside an SLF function. |
|
|
807 | |
|
|
808 | The latter two basically mean that the thread isn't currently inside a |
|
|
809 | perl callback called from some C function (usually via some XS modules) |
|
|
810 | and isn't currently executing inside some C function itself (via Coro's XS |
|
|
811 | API). |
|
|
812 | |
|
|
813 | This call returns true when it could cancel the thread, or croaks with an |
|
|
814 | error otherwise (i.e. it either returns true or doesn't return at all). |
|
|
815 | |
|
|
816 | Why the weird interface? Well, there are two common models on how and |
|
|
817 | when to cancel things. In the first, you have the expectation that your |
|
|
818 | coro thread can be cancelled when you want to cancel it - if the thread |
|
|
819 | isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >> |
|
|
820 | croaks to notify of the bug. |
|
|
821 | |
|
|
822 | In the second model you sometimes want to ask nicely to cancel a thread, |
|
|
823 | but if it's not a good time, well, then don't cancel. This can be done |
|
|
824 | relatively easy like this: |
|
|
825 | |
|
|
826 | if (! eval { $coro->safe_cancel }) { |
|
|
827 | warn "unable to cancel thread: $@"; |
402 | } |
828 | } |
403 | } |
|
|
404 | |
829 | |
405 | =item $coroutine->join |
830 | However, what you never should do is first try to cancel "safely" and |
|
|
831 | if that fails, cancel the "hard" way with C<< ->cancel >>. That makes |
|
|
832 | no sense: either you rely on being able to execute cleanup code in your |
|
|
833 | thread context, or you don't. If you do, then C<< ->safe_cancel >> is the |
|
|
834 | only way, and if you don't, then C<< ->cancel >> is always faster and more |
|
|
835 | direct. |
406 | |
836 | |
407 | Wait until the coroutine terminates and return any values given to the |
837 | =item $coro->schedule_to |
408 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
|
|
409 | from multiple coroutines. |
|
|
410 | |
838 | |
411 | =cut |
839 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
|
|
840 | of continuing with the next coro from the ready queue, always switch to |
|
|
841 | the given coro object (regardless of priority etc.). The readyness |
|
|
842 | state of that coro isn't changed. |
412 | |
843 | |
413 | sub join { |
844 | This is an advanced method for special cases - I'd love to hear about any |
414 | my $self = shift; |
845 | uses for this one. |
415 | |
846 | |
416 | unless ($self->{_status}) { |
847 | =item $coro->cede_to |
417 | my $current = $current; |
|
|
418 | |
848 | |
419 | push @{$self->{_on_destroy}}, sub { |
849 | Like C<schedule_to>, but puts the current coro into the ready |
420 | $current->ready; |
850 | queue. This has the effect of temporarily switching to the given |
421 | undef $current; |
851 | coro, and continuing some time later. |
422 | }; |
|
|
423 | |
852 | |
424 | &schedule while $current; |
853 | This is an advanced method for special cases - I'd love to hear about any |
425 | } |
854 | uses for this one. |
426 | |
855 | |
427 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
|
|
428 | } |
|
|
429 | |
|
|
430 | =item $coroutine->on_destroy (\&cb) |
|
|
431 | |
|
|
432 | Registers a callback that is called when this coroutine gets destroyed, |
|
|
433 | but before it is joined. The callback gets passed the terminate arguments, |
|
|
434 | if any. |
|
|
435 | |
|
|
436 | =cut |
|
|
437 | |
|
|
438 | sub on_destroy { |
|
|
439 | my ($self, $cb) = @_; |
|
|
440 | |
|
|
441 | push @{ $self->{_on_destroy} }, $cb; |
|
|
442 | } |
|
|
443 | |
|
|
444 | =item $oldprio = $coroutine->prio ($newprio) |
|
|
445 | |
|
|
446 | Sets (or gets, if the argument is missing) the priority of the |
|
|
447 | coroutine. Higher priority coroutines get run before lower priority |
|
|
448 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
|
|
449 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
|
|
450 | to get then): |
|
|
451 | |
|
|
452 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
|
|
453 | 3 > 1 > 0 > -1 > -3 > -4 |
|
|
454 | |
|
|
455 | # set priority to HIGH |
|
|
456 | current->prio(PRIO_HIGH); |
|
|
457 | |
|
|
458 | The idle coroutine ($Coro::idle) always has a lower priority than any |
|
|
459 | existing coroutine. |
|
|
460 | |
|
|
461 | Changing the priority of the current coroutine will take effect immediately, |
|
|
462 | but changing the priority of coroutines in the ready queue (but not |
|
|
463 | running) will only take effect after the next schedule (of that |
|
|
464 | coroutine). This is a bug that will be fixed in some future version. |
|
|
465 | |
|
|
466 | =item $newprio = $coroutine->nice ($change) |
|
|
467 | |
|
|
468 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
|
|
469 | higher values mean lower priority, just as in unix). |
|
|
470 | |
|
|
471 | =item $olddesc = $coroutine->desc ($newdesc) |
|
|
472 | |
|
|
473 | Sets (or gets in case the argument is missing) the description for this |
|
|
474 | coroutine. This is just a free-form string you can associate with a coroutine. |
|
|
475 | |
|
|
476 | This method simply sets the C<< $coroutine->{desc} >> member to the given string. You |
|
|
477 | can modify this member directly if you wish. |
|
|
478 | |
|
|
479 | =item $coroutine->throw ([$scalar]) |
856 | =item $coro->throw ([$scalar]) |
480 | |
857 | |
481 | If C<$throw> is specified and defined, it will be thrown as an exception |
858 | If C<$throw> is specified and defined, it will be thrown as an exception |
482 | inside the coroutine at the next convinient point in time (usually after |
859 | inside the coro at the next convenient point in time. Otherwise |
483 | it gains control at the next schedule/transfer/cede). Otherwise clears the |
|
|
484 | exception object. |
860 | clears the exception object. |
|
|
861 | |
|
|
862 | Coro will check for the exception each time a schedule-like-function |
|
|
863 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
|
|
864 | >>, C<< Coro::Handle->readable >> and so on. Most of those functions (all |
|
|
865 | that are part of Coro itself) detect this case and return early in case an |
|
|
866 | exception is pending. |
485 | |
867 | |
486 | The exception object will be thrown "as is" with the specified scalar in |
868 | The exception object will be thrown "as is" with the specified scalar in |
487 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
869 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
488 | (unlike with C<die>). |
870 | (unlike with C<die>). |
489 | |
871 | |
490 | This can be used as a softer means than C<cancel> to ask a coroutine to |
872 | This can be used as a softer means than either C<cancel> or C<safe_cancel |
491 | end itself, although there is no guarentee that the exception will lead to |
873 | >to ask a coro to end itself, although there is no guarantee that the |
492 | termination, and if the exception isn't caught it might well end the whole |
874 | exception will lead to termination, and if the exception isn't caught it |
493 | program. |
875 | might well end the whole program. |
|
|
876 | |
|
|
877 | You might also think of C<throw> as being the moral equivalent of |
|
|
878 | C<kill>ing a coro with a signal (in this case, a scalar). |
|
|
879 | |
|
|
880 | =item $coro->join |
|
|
881 | |
|
|
882 | Wait until the coro terminates and return any values given to the |
|
|
883 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
|
|
884 | from multiple threads, and all will be resumed and given the status |
|
|
885 | return once the C<$coro> terminates. |
|
|
886 | |
|
|
887 | =item $coro->on_destroy (\&cb) |
|
|
888 | |
|
|
889 | Registers a callback that is called when this coro thread gets destroyed, |
|
|
890 | that is, after it's resources have been freed but before it is joined. The |
|
|
891 | callback gets passed the terminate/cancel arguments, if any, and I<must |
|
|
892 | not> die, under any circumstances. |
|
|
893 | |
|
|
894 | There can be any number of C<on_destroy> callbacks per coro, and there is |
|
|
895 | no way currently to remove a callback once added. |
|
|
896 | |
|
|
897 | =item $oldprio = $coro->prio ($newprio) |
|
|
898 | |
|
|
899 | Sets (or gets, if the argument is missing) the priority of the |
|
|
900 | coro thread. Higher priority coro get run before lower priority |
|
|
901 | coros. Priorities are small signed integers (currently -4 .. +3), |
|
|
902 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
|
|
903 | to get then): |
|
|
904 | |
|
|
905 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
|
|
906 | 3 > 1 > 0 > -1 > -3 > -4 |
|
|
907 | |
|
|
908 | # set priority to HIGH |
|
|
909 | current->prio (PRIO_HIGH); |
|
|
910 | |
|
|
911 | The idle coro thread ($Coro::idle) always has a lower priority than any |
|
|
912 | existing coro. |
|
|
913 | |
|
|
914 | Changing the priority of the current coro will take effect immediately, |
|
|
915 | but changing the priority of a coro in the ready queue (but not running) |
|
|
916 | will only take effect after the next schedule (of that coro). This is a |
|
|
917 | bug that will be fixed in some future version. |
|
|
918 | |
|
|
919 | =item $newprio = $coro->nice ($change) |
|
|
920 | |
|
|
921 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
|
|
922 | higher values mean lower priority, just as in UNIX's nice command). |
|
|
923 | |
|
|
924 | =item $olddesc = $coro->desc ($newdesc) |
|
|
925 | |
|
|
926 | Sets (or gets in case the argument is missing) the description for this |
|
|
927 | coro thread. This is just a free-form string you can associate with a |
|
|
928 | coro. |
|
|
929 | |
|
|
930 | This method simply sets the C<< $coro->{desc} >> member to the given |
|
|
931 | string. You can modify this member directly if you wish, and in fact, this |
|
|
932 | is often preferred to indicate major processing states that cna then be |
|
|
933 | seen for example in a L<Coro::Debug> session: |
|
|
934 | |
|
|
935 | sub my_long_function { |
|
|
936 | local $Coro::current->{desc} = "now in my_long_function"; |
|
|
937 | ... |
|
|
938 | $Coro::current->{desc} = "my_long_function: phase 1"; |
|
|
939 | ... |
|
|
940 | $Coro::current->{desc} = "my_long_function: phase 2"; |
|
|
941 | ... |
|
|
942 | } |
494 | |
943 | |
495 | =cut |
944 | =cut |
496 | |
945 | |
497 | sub desc { |
946 | sub desc { |
498 | my $old = $_[0]{desc}; |
947 | my $old = $_[0]{desc}; |
499 | $_[0]{desc} = $_[1] if @_ > 1; |
948 | $_[0]{desc} = $_[1] if @_ > 1; |
500 | $old; |
949 | $old; |
501 | } |
950 | } |
502 | |
951 | |
|
|
952 | sub transfer { |
|
|
953 | require Carp; |
|
|
954 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
955 | } |
|
|
956 | |
503 | =back |
957 | =back |
504 | |
958 | |
505 | =head2 GLOBAL FUNCTIONS |
959 | =head1 GLOBAL FUNCTIONS |
506 | |
960 | |
507 | =over 4 |
961 | =over 4 |
508 | |
962 | |
509 | =item Coro::nready |
963 | =item Coro::nready |
510 | |
964 | |
511 | Returns the number of coroutines that are currently in the ready state, |
965 | Returns the number of coro that are currently in the ready state, |
512 | i.e. that can be switched to. The value C<0> means that the only runnable |
966 | i.e. that can be switched to by calling C<schedule> directory or |
|
|
967 | indirectly. The value C<0> means that the only runnable coro is the |
513 | coroutine is the currently running one, so C<cede> would have no effect, |
968 | currently running one, so C<cede> would have no effect, and C<schedule> |
514 | and C<schedule> would cause a deadlock unless there is an idle handler |
969 | would cause a deadlock unless there is an idle handler that wakes up some |
515 | that wakes up some coroutines. |
970 | coro. |
516 | |
971 | |
517 | =item my $guard = Coro::guard { ... } |
972 | =item my $guard = Coro::guard { ... } |
518 | |
973 | |
519 | This creates and returns a guard object. Nothing happens until the object |
974 | This function still exists, but is deprecated. Please use the |
520 | gets destroyed, in which case the codeblock given as argument will be |
975 | C<Guard::guard> function instead. |
521 | executed. This is useful to free locks or other resources in case of a |
|
|
522 | runtime error or when the coroutine gets canceled, as in both cases the |
|
|
523 | guard block will be executed. The guard object supports only one method, |
|
|
524 | C<< ->cancel >>, which will keep the codeblock from being executed. |
|
|
525 | |
|
|
526 | Example: set some flag and clear it again when the coroutine gets canceled |
|
|
527 | or the function returns: |
|
|
528 | |
|
|
529 | sub do_something { |
|
|
530 | my $guard = Coro::guard { $busy = 0 }; |
|
|
531 | $busy = 1; |
|
|
532 | |
|
|
533 | # do something that requires $busy to be true |
|
|
534 | } |
|
|
535 | |
976 | |
536 | =cut |
977 | =cut |
537 | |
978 | |
538 | sub guard(&) { |
979 | BEGIN { *guard = \&Guard::guard } |
539 | bless \(my $cb = $_[0]), "Coro::guard" |
|
|
540 | } |
|
|
541 | |
|
|
542 | sub Coro::guard::cancel { |
|
|
543 | ${$_[0]} = sub { }; |
|
|
544 | } |
|
|
545 | |
|
|
546 | sub Coro::guard::DESTROY { |
|
|
547 | ${$_[0]}->(); |
|
|
548 | } |
|
|
549 | |
|
|
550 | |
980 | |
551 | =item unblock_sub { ... } |
981 | =item unblock_sub { ... } |
552 | |
982 | |
553 | This utility function takes a BLOCK or code reference and "unblocks" it, |
983 | This utility function takes a BLOCK or code reference and "unblocks" it, |
554 | returning the new coderef. This means that the new coderef will return |
984 | returning a new coderef. Unblocking means that calling the new coderef |
555 | immediately without blocking, returning nothing, while the original code |
985 | will return immediately without blocking, returning nothing, while the |
556 | ref will be called (with parameters) from within its own coroutine. |
986 | original code ref will be called (with parameters) from within another |
|
|
987 | coro. |
557 | |
988 | |
558 | The reason this function exists is that many event libraries (such as the |
989 | The reason this function exists is that many event libraries (such as |
559 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
990 | the venerable L<Event|Event> module) are not thread-safe (a weaker form |
560 | of thread-safety). This means you must not block within event callbacks, |
991 | of reentrancy). This means you must not block within event callbacks, |
561 | otherwise you might suffer from crashes or worse. |
992 | otherwise you might suffer from crashes or worse. The only event library |
|
|
993 | currently known that is safe to use without C<unblock_sub> is L<EV> (but |
|
|
994 | you might still run into deadlocks if all event loops are blocked). |
|
|
995 | |
|
|
996 | Coro will try to catch you when you block in the event loop |
|
|
997 | ("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
|
|
998 | only works when you do not run your own event loop. |
562 | |
999 | |
563 | This function allows your callbacks to block by executing them in another |
1000 | This function allows your callbacks to block by executing them in another |
564 | coroutine where it is safe to block. One example where blocking is handy |
1001 | coro where it is safe to block. One example where blocking is handy |
565 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
1002 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
566 | disk. |
1003 | disk, for example. |
567 | |
1004 | |
568 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
1005 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
569 | creating event callbacks that want to block. |
1006 | creating event callbacks that want to block. |
|
|
1007 | |
|
|
1008 | If your handler does not plan to block (e.g. simply sends a message to |
|
|
1009 | another coro, or puts some other coro into the ready queue), there is |
|
|
1010 | no reason to use C<unblock_sub>. |
|
|
1011 | |
|
|
1012 | Note that you also need to use C<unblock_sub> for any other callbacks that |
|
|
1013 | are indirectly executed by any C-based event loop. For example, when you |
|
|
1014 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
|
|
1015 | provides callbacks that are the result of some event callback, then you |
|
|
1016 | must not block either, or use C<unblock_sub>. |
570 | |
1017 | |
571 | =cut |
1018 | =cut |
572 | |
1019 | |
573 | our @unblock_queue; |
1020 | our @unblock_queue; |
574 | |
1021 | |
… | |
… | |
577 | # return immediately and can be reused) and because we cannot cede |
1024 | # return immediately and can be reused) and because we cannot cede |
578 | # inside an event callback. |
1025 | # inside an event callback. |
579 | our $unblock_scheduler = new Coro sub { |
1026 | our $unblock_scheduler = new Coro sub { |
580 | while () { |
1027 | while () { |
581 | while (my $cb = pop @unblock_queue) { |
1028 | while (my $cb = pop @unblock_queue) { |
582 | # this is an inlined copy of async_pool |
1029 | &async_pool (@$cb); |
583 | my $coro = (pop @async_pool) || new Coro \&pool_handler; |
|
|
584 | |
1030 | |
585 | $coro->{_invoke} = $cb; |
|
|
586 | $coro->ready; |
|
|
587 | cede; # for short-lived callbacks, this reduces pressure on the coro pool |
1031 | # for short-lived callbacks, this reduces pressure on the coro pool |
|
|
1032 | # as the chance is very high that the async_poll coro will be back |
|
|
1033 | # in the idle state when cede returns |
|
|
1034 | cede; |
588 | } |
1035 | } |
589 | schedule; # sleep well |
1036 | schedule; # sleep well |
590 | } |
1037 | } |
591 | }; |
1038 | }; |
592 | $unblock_scheduler->desc ("[unblock_sub scheduler]"); |
1039 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
593 | |
1040 | |
594 | sub unblock_sub(&) { |
1041 | sub unblock_sub(&) { |
595 | my $cb = shift; |
1042 | my $cb = shift; |
596 | |
1043 | |
597 | sub { |
1044 | sub { |
598 | unshift @unblock_queue, [$cb, @_]; |
1045 | unshift @unblock_queue, [$cb, @_]; |
599 | $unblock_scheduler->ready; |
1046 | $unblock_scheduler->ready; |
600 | } |
1047 | } |
601 | } |
1048 | } |
602 | |
1049 | |
|
|
1050 | =item $cb = rouse_cb |
|
|
1051 | |
|
|
1052 | Create and return a "rouse callback". That's a code reference that, |
|
|
1053 | when called, will remember a copy of its arguments and notify the owner |
|
|
1054 | coro of the callback. |
|
|
1055 | |
|
|
1056 | See the next function. |
|
|
1057 | |
|
|
1058 | =item @args = rouse_wait [$cb] |
|
|
1059 | |
|
|
1060 | Wait for the specified rouse callback (or the last one that was created in |
|
|
1061 | this coro). |
|
|
1062 | |
|
|
1063 | As soon as the callback is invoked (or when the callback was invoked |
|
|
1064 | before C<rouse_wait>), it will return the arguments originally passed to |
|
|
1065 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
1066 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
1067 | statement at the end. |
|
|
1068 | |
|
|
1069 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
|
|
1070 | |
603 | =back |
1071 | =back |
604 | |
1072 | |
605 | =cut |
1073 | =cut |
606 | |
1074 | |
|
|
1075 | for my $module (qw(Channel RWLock Semaphore SemaphoreSet Signal Specific)) { |
|
|
1076 | my $old = defined &{"Coro::$module\::new"} && \&{"Coro::$module\::new"}; |
|
|
1077 | |
|
|
1078 | *{"Coro::$module\::new"} = sub { |
|
|
1079 | require "Coro/$module.pm"; |
|
|
1080 | |
|
|
1081 | # some modules have their new predefined in State.xs, some don't |
|
|
1082 | *{"Coro::$module\::new"} = $old |
|
|
1083 | if $old; |
|
|
1084 | |
|
|
1085 | goto &{"Coro::$module\::new"}; |
|
|
1086 | }; |
|
|
1087 | } |
|
|
1088 | |
607 | 1; |
1089 | 1; |
608 | |
1090 | |
|
|
1091 | =head1 HOW TO WAIT FOR A CALLBACK |
|
|
1092 | |
|
|
1093 | It is very common for a coro to wait for some callback to be |
|
|
1094 | called. This occurs naturally when you use coro in an otherwise |
|
|
1095 | event-based program, or when you use event-based libraries. |
|
|
1096 | |
|
|
1097 | These typically register a callback for some event, and call that callback |
|
|
1098 | when the event occured. In a coro, however, you typically want to |
|
|
1099 | just wait for the event, simplyifying things. |
|
|
1100 | |
|
|
1101 | For example C<< AnyEvent->child >> registers a callback to be called when |
|
|
1102 | a specific child has exited: |
|
|
1103 | |
|
|
1104 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
1105 | |
|
|
1106 | But from within a coro, you often just want to write this: |
|
|
1107 | |
|
|
1108 | my $status = wait_for_child $pid; |
|
|
1109 | |
|
|
1110 | Coro offers two functions specifically designed to make this easy, |
|
|
1111 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
|
|
1112 | |
|
|
1113 | The first function, C<rouse_cb>, generates and returns a callback that, |
|
|
1114 | when invoked, will save its arguments and notify the coro that |
|
|
1115 | created the callback. |
|
|
1116 | |
|
|
1117 | The second function, C<rouse_wait>, waits for the callback to be called |
|
|
1118 | (by calling C<schedule> to go to sleep) and returns the arguments |
|
|
1119 | originally passed to the callback. |
|
|
1120 | |
|
|
1121 | Using these functions, it becomes easy to write the C<wait_for_child> |
|
|
1122 | function mentioned above: |
|
|
1123 | |
|
|
1124 | sub wait_for_child($) { |
|
|
1125 | my ($pid) = @_; |
|
|
1126 | |
|
|
1127 | my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
|
|
1128 | |
|
|
1129 | my ($rpid, $rstatus) = Coro::rouse_wait; |
|
|
1130 | $rstatus |
|
|
1131 | } |
|
|
1132 | |
|
|
1133 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
|
|
1134 | you can roll your own, using C<schedule>: |
|
|
1135 | |
|
|
1136 | sub wait_for_child($) { |
|
|
1137 | my ($pid) = @_; |
|
|
1138 | |
|
|
1139 | # store the current coro in $current, |
|
|
1140 | # and provide result variables for the closure passed to ->child |
|
|
1141 | my $current = $Coro::current; |
|
|
1142 | my ($done, $rstatus); |
|
|
1143 | |
|
|
1144 | # pass a closure to ->child |
|
|
1145 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
1146 | $rstatus = $_[1]; # remember rstatus |
|
|
1147 | $done = 1; # mark $rstatus as valud |
|
|
1148 | }); |
|
|
1149 | |
|
|
1150 | # wait until the closure has been called |
|
|
1151 | schedule while !$done; |
|
|
1152 | |
|
|
1153 | $rstatus |
|
|
1154 | } |
|
|
1155 | |
|
|
1156 | |
609 | =head1 BUGS/LIMITATIONS |
1157 | =head1 BUGS/LIMITATIONS |
610 | |
1158 | |
611 | - you must make very sure that no coro is still active on global |
1159 | =over 4 |
612 | destruction. very bad things might happen otherwise (usually segfaults). |
|
|
613 | |
1160 | |
|
|
1161 | =item fork with pthread backend |
|
|
1162 | |
|
|
1163 | When Coro is compiled using the pthread backend (which isn't recommended |
|
|
1164 | but required on many BSDs as their libcs are completely broken), then |
|
|
1165 | coro will not survive a fork. There is no known workaround except to |
|
|
1166 | fix your libc and use a saner backend. |
|
|
1167 | |
|
|
1168 | =item perl process emulation ("threads") |
|
|
1169 | |
614 | - this module is not thread-safe. You should only ever use this module |
1170 | This module is not perl-pseudo-thread-safe. You should only ever use this |
615 | from the same thread (this requirement might be loosened in the future |
1171 | module from the first thread (this requirement might be removed in the |
616 | to allow per-thread schedulers, but Coro::State does not yet allow |
1172 | future to allow per-thread schedulers, but Coro::State does not yet allow |
617 | this). |
1173 | this). I recommend disabling thread support and using processes, as having |
|
|
1174 | the windows process emulation enabled under unix roughly halves perl |
|
|
1175 | performance, even when not used. |
|
|
1176 | |
|
|
1177 | Attempts to use threads created in another emulated process will crash |
|
|
1178 | ("cleanly", with a null pointer exception). |
|
|
1179 | |
|
|
1180 | =item coro switching is not signal safe |
|
|
1181 | |
|
|
1182 | You must not switch to another coro from within a signal handler (only |
|
|
1183 | relevant with %SIG - most event libraries provide safe signals), I<unless> |
|
|
1184 | you are sure you are not interrupting a Coro function. |
|
|
1185 | |
|
|
1186 | That means you I<MUST NOT> call any function that might "block" the |
|
|
1187 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
|
|
1188 | anything that calls those. Everything else, including calling C<ready>, |
|
|
1189 | works. |
|
|
1190 | |
|
|
1191 | =back |
|
|
1192 | |
|
|
1193 | |
|
|
1194 | =head1 WINDOWS PROCESS EMULATION |
|
|
1195 | |
|
|
1196 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
1197 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
1198 | while in the same mail making rather confused statements about perl |
|
|
1199 | ithreads (for example, that memory or files would be shared), showing his |
|
|
1200 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
1201 | it is probably not obvious to everybody). |
|
|
1202 | |
|
|
1203 | What follows is an ultra-condensed version of my talk about threads in |
|
|
1204 | scripting languages given on the perl workshop 2009: |
|
|
1205 | |
|
|
1206 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
1207 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
1208 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
1209 | |
|
|
1210 | It does that by using threads instead of OS processes. The difference |
|
|
1211 | between processes and threads is that threads share memory (and other |
|
|
1212 | state, such as files) between threads within a single process, while |
|
|
1213 | processes do not share anything (at least not semantically). That |
|
|
1214 | means that modifications done by one thread are seen by others, while |
|
|
1215 | modifications by one process are not seen by other processes. |
|
|
1216 | |
|
|
1217 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
1218 | process, all state is copied (memory is copied physically, files and code |
|
|
1219 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
1220 | the same behaviour can be achieved by using operating system processes, |
|
|
1221 | except that UNIX typically uses hardware built into the system to do this |
|
|
1222 | efficiently, while the windows process emulation emulates this hardware in |
|
|
1223 | software (rather efficiently, but of course it is still much slower than |
|
|
1224 | dedicated hardware). |
|
|
1225 | |
|
|
1226 | As mentioned before, loading code, modifying code, modifying data |
|
|
1227 | structures and so on is only visible in the ithreads process doing the |
|
|
1228 | modification, not in other ithread processes within the same OS process. |
|
|
1229 | |
|
|
1230 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
1231 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
1232 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
1233 | by the forks module, which gives you the (i-) threads API, just much |
|
|
1234 | faster). |
|
|
1235 | |
|
|
1236 | Sharing data is in the i-threads model is done by transfering data |
|
|
1237 | structures between threads using copying semantics, which is very slow - |
|
|
1238 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
1239 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
1240 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
1241 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
1242 | real threads, refer to my talk for details). |
|
|
1243 | |
|
|
1244 | As summary, i-threads *use* threads to implement processes, while |
|
|
1245 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
1246 | processes. I-threads slow down every perl program when enabled, and |
|
|
1247 | outside of windows, serve no (or little) practical purpose, but |
|
|
1248 | disadvantages every single-threaded Perl program. |
|
|
1249 | |
|
|
1250 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
1251 | misleading as it implies that it implements some kind of thread model for |
|
|
1252 | perl, and prefer the name "windows process emulation", which describes the |
|
|
1253 | actual use and behaviour of it much better. |
618 | |
1254 | |
619 | =head1 SEE ALSO |
1255 | =head1 SEE ALSO |
620 | |
1256 | |
621 | Lower level Configuration, Coroutine Environment: L<Coro::State>. |
1257 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
622 | |
1258 | |
623 | Debugging: L<Coro::Debug>. |
1259 | Debugging: L<Coro::Debug>. |
624 | |
1260 | |
625 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
1261 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
626 | |
1262 | |
627 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
1263 | Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
1264 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
628 | |
1265 | |
629 | Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>. |
1266 | I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
630 | |
1267 | |
631 | Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>. |
1268 | Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
1269 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
1270 | L<Coro::Select>. |
632 | |
1271 | |
633 | Embedding: L<Coro::MakeMaker>. |
1272 | XS API: L<Coro::MakeMaker>. |
|
|
1273 | |
|
|
1274 | Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
634 | |
1275 | |
635 | =head1 AUTHOR |
1276 | =head1 AUTHOR |
636 | |
1277 | |
637 | Marc Lehmann <schmorp@schmorp.de> |
1278 | Marc Lehmann <schmorp@schmorp.de> |
638 | http://home.schmorp.de/ |
1279 | http://home.schmorp.de/ |