1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | Coro - coroutine process abstraction |
3 | Coro - the only real threads in perl |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | use Coro; |
7 | use Coro; |
8 | |
8 | |
9 | async { |
9 | async { |
10 | # some asynchronous thread of execution |
10 | # some asynchronous thread of execution |
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11 | print "2\n"; |
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12 | cede; # yield back to main |
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13 | print "4\n"; |
11 | }; |
14 | }; |
12 | |
15 | print "1\n"; |
13 | # alternatively create an async coroutine like this: |
16 | cede; # yield to coro |
14 | |
17 | print "3\n"; |
15 | sub some_func : Coro { |
18 | cede; # and again |
16 | # some more async code |
19 | |
17 | } |
20 | # use locking |
18 | |
21 | use Coro::Semaphore; |
19 | cede; |
22 | my $lock = new Coro::Semaphore; |
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23 | my $locked; |
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24 | |
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25 | $lock->down; |
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26 | $locked = 1; |
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27 | $lock->up; |
20 | |
28 | |
21 | =head1 DESCRIPTION |
29 | =head1 DESCRIPTION |
22 | |
30 | |
23 | This module collection manages coroutines. Coroutines are similar to |
31 | For a tutorial-style introduction, please read the L<Coro::Intro> |
24 | threads but don't run in parallel. |
32 | manpage. This manpage mainly contains reference information. |
25 | |
33 | |
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34 | This module collection manages continuations in general, most often in |
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35 | the form of cooperative threads (also called coros, or simply "coro" |
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36 | in the documentation). They are similar to kernel threads but don't (in |
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37 | general) run in parallel at the same time even on SMP machines. The |
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38 | specific flavor of thread offered by this module also guarantees you that |
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39 | it will not switch between threads unless necessary, at easily-identified |
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40 | points in your program, so locking and parallel access are rarely an |
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41 | issue, making thread programming much safer and easier than using other |
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42 | thread models. |
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43 | |
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44 | Unlike the so-called "Perl threads" (which are not actually real threads |
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45 | but only the windows process emulation (see section of same name for more |
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46 | details) ported to unix, and as such act as processes), Coro provides |
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47 | a full shared address space, which makes communication between threads |
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48 | very easy. And Coro's threads are fast, too: disabling the Windows |
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49 | process emulation code in your perl and using Coro can easily result in |
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50 | a two to four times speed increase for your programs. A parallel matrix |
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51 | multiplication benchmark runs over 300 times faster on a single core than |
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52 | perl's pseudo-threads on a quad core 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 | |
26 | In this module, coroutines are defined as "callchain + lexical variables |
60 | In this module, a thread is defined as "callchain + lexical variables + |
27 | + @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own |
61 | some package variables + C stack), that is, a thread has its own callchain, |
28 | callchain, it's own set of lexicals and it's own set of perl's most |
62 | its own set of lexicals and its own set of perls most important global |
29 | important global variables. |
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. |
30 | |
67 | |
31 | =cut |
68 | =cut |
32 | |
69 | |
33 | package Coro; |
70 | package Coro; |
34 | |
71 | |
35 | use strict; |
72 | use common::sense; |
36 | no warnings "uninitialized"; |
73 | |
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74 | use Carp (); |
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75 | |
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76 | use Guard (); |
37 | |
77 | |
38 | use Coro::State; |
78 | use Coro::State; |
39 | |
79 | |
40 | use base qw(Coro::State Exporter); |
80 | use base qw(Coro::State Exporter); |
41 | |
81 | |
42 | our $idle; # idle handler |
82 | our $idle; # idle handler |
43 | our $main; # main coroutine |
83 | our $main; # main coro |
44 | our $current; # current coroutine |
84 | our $current; # current coro |
45 | |
85 | |
46 | our $VERSION = '3.01'; |
86 | our $VERSION = 5.17; |
47 | |
87 | |
48 | our @EXPORT = qw(async cede schedule terminate current unblock_sub); |
88 | our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
49 | our %EXPORT_TAGS = ( |
89 | our %EXPORT_TAGS = ( |
50 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
90 | prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
51 | ); |
91 | ); |
52 | our @EXPORT_OK = @{$EXPORT_TAGS{prio}}; |
92 | our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
53 | |
93 | |
54 | { |
94 | =head1 GLOBAL VARIABLES |
55 | my @async; |
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56 | my $init; |
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57 | |
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58 | # this way of handling attributes simply is NOT scalable ;() |
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59 | sub import { |
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60 | no strict 'refs'; |
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61 | |
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62 | Coro->export_to_level (1, @_); |
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63 | |
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64 | my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; |
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65 | *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { |
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66 | my ($package, $ref) = (shift, shift); |
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67 | my @attrs; |
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68 | for (@_) { |
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69 | if ($_ eq "Coro") { |
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70 | push @async, $ref; |
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71 | unless ($init++) { |
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72 | eval q{ |
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73 | sub INIT { |
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74 | &async(pop @async) while @async; |
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75 | } |
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76 | }; |
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77 | } |
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78 | } else { |
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79 | push @attrs, $_; |
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80 | } |
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81 | } |
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82 | return $old ? $old->($package, $ref, @attrs) : @attrs; |
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83 | }; |
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84 | } |
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85 | |
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86 | } |
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87 | |
95 | |
88 | =over 4 |
96 | =over 4 |
89 | |
97 | |
90 | =item $main |
98 | =item $Coro::main |
91 | |
99 | |
92 | This coroutine represents the main program. |
100 | This variable stores the Coro object that represents the main |
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101 | program. While you cna C<ready> it and do most other things you can do to |
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102 | coro, it is mainly useful to compare again C<$Coro::current>, to see |
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103 | whether you are running in the main program or not. |
93 | |
104 | |
94 | =cut |
105 | =cut |
95 | |
106 | |
96 | $main = new Coro; |
107 | # $main is now being initialised by Coro::State |
97 | |
108 | |
98 | =item $current (or as function: current) |
109 | =item $Coro::current |
99 | |
110 | |
100 | The current coroutine (the last coroutine switched to). The initial value |
111 | The Coro object representing the current coro (the last |
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112 | coro that the Coro scheduler switched to). The initial value is |
101 | is C<$main> (of course). |
113 | C<$Coro::main> (of course). |
102 | |
114 | |
103 | This variable is B<strictly> I<read-only>. It is provided for performance |
115 | This variable is B<strictly> I<read-only>. You can take copies of the |
104 | reasons. If performance is not essentiel you are encouraged to use the |
116 | value stored in it and use it as any other Coro object, but you must |
105 | C<Coro::current> function instead. |
117 | not otherwise modify the variable itself. |
106 | |
118 | |
107 | =cut |
119 | =cut |
108 | |
120 | |
109 | # maybe some other module used Coro::Specific before... |
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110 | $main->{specific} = $current->{specific} |
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111 | if $current; |
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112 | |
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113 | _set_current $main; |
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114 | |
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115 | sub current() { $current } |
121 | sub current() { $current } # [DEPRECATED] |
116 | |
122 | |
117 | =item $idle |
123 | =item $Coro::idle |
118 | |
124 | |
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125 | This variable is mainly useful to integrate Coro into event loops. It is |
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126 | usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
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127 | pretty low-level functionality. |
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128 | |
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129 | This variable stores either a Coro object or a callback. |
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130 | |
119 | A callback that is called whenever the scheduler finds no ready coroutines |
131 | If it is a callback, the it is called whenever the scheduler finds no |
120 | to run. The default implementation prints "FATAL: deadlock detected" and |
132 | ready coros to run. The default implementation prints "FATAL: |
121 | exits, because the program has no other way to continue. |
133 | deadlock detected" and exits, because the program has no other way to |
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134 | continue. |
122 | |
135 | |
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136 | If it is a coro object, then this object will be readied (without |
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137 | invoking any ready hooks, however) when the scheduler finds no other ready |
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138 | coros to run. |
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139 | |
123 | This hook is overwritten by modules such as C<Coro::Timer> and |
140 | This hook is overwritten by modules such as C<Coro::EV> and |
124 | C<Coro::Event> to wait on an external event that hopefully wake up a |
141 | C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
125 | coroutine so the scheduler can run it. |
142 | coro so the scheduler can run it. |
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143 | |
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144 | Note that the callback I<must not>, under any circumstances, block |
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145 | the current coro. Normally, this is achieved by having an "idle |
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146 | coro" that calls the event loop and then blocks again, and then |
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147 | readying that coro in the idle handler, or by simply placing the idle |
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148 | coro in this variable. |
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149 | |
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150 | See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
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151 | technique. |
126 | |
152 | |
127 | Please note that if your callback recursively invokes perl (e.g. for event |
153 | Please note that if your callback recursively invokes perl (e.g. for event |
128 | handlers), then it must be prepared to be called recursively. |
154 | handlers), then it must be prepared to be called recursively itself. |
129 | |
155 | |
130 | =cut |
156 | =cut |
131 | |
157 | |
132 | $idle = sub { |
158 | $idle = sub { |
133 | print STDERR "FATAL: deadlock detected\n"; |
159 | warn "oi\n";#d# |
134 | exit (51); |
160 | Carp::confess ("FATAL: deadlock detected"); |
135 | }; |
161 | }; |
136 | |
162 | |
137 | # this coroutine is necessary because a coroutine |
163 | # this coro is necessary because a coro |
138 | # cannot destroy itself. |
164 | # cannot destroy itself. |
139 | my @destroy; |
165 | our @destroy; |
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166 | our $manager; |
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167 | |
140 | my $manager; $manager = new Coro sub { |
168 | $manager = new Coro sub { |
141 | while () { |
169 | while () { |
142 | # by overwriting the state object with the manager we destroy it |
170 | Coro::State::cancel shift @destroy |
143 | # while still being able to schedule this coroutine (in case it has |
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144 | # been readied multiple times. this is harmless since the manager |
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145 | # can be called as many times as neccessary and will always |
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146 | # remove itself from the runqueue |
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147 | while (@destroy) { |
171 | while @destroy; |
148 | my $coro = pop @destroy; |
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149 | $coro->{status} ||= []; |
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150 | $_->ready for @{delete $coro->{join} || []}; |
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151 | |
172 | |
152 | # the next line destroys the coro state, but keeps the |
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153 | # coroutine itself intact (we basically make it a zombie |
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154 | # coroutine that always runs the manager thread, so it's possible |
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155 | # to transfer() to this coroutine). |
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156 | $coro->_clone_state_from ($manager); |
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157 | } |
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158 | &schedule; |
173 | &schedule; |
159 | } |
174 | } |
160 | }; |
175 | }; |
161 | |
176 | $manager->{desc} = "[coro manager]"; |
162 | # static methods. not really. |
177 | $manager->prio (PRIO_MAX); |
163 | |
178 | |
164 | =back |
179 | =back |
165 | |
180 | |
166 | =head2 STATIC METHODS |
181 | =head1 SIMPLE CORO CREATION |
167 | |
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168 | Static methods are actually functions that operate on the current coroutine only. |
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169 | |
182 | |
170 | =over 4 |
183 | =over 4 |
171 | |
184 | |
172 | =item async { ... } [@args...] |
185 | =item async { ... } [@args...] |
173 | |
186 | |
174 | Create a new asynchronous coroutine and return it's coroutine object |
187 | Create a new coro and return its Coro object (usually |
175 | (usually unused). When the sub returns the new coroutine is automatically |
188 | unused). The coro will be put into the ready queue, so |
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189 | it will start running automatically on the next scheduler run. |
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190 | |
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191 | The first argument is a codeblock/closure that should be executed in the |
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192 | coro. When it returns argument returns the coro is automatically |
176 | terminated. |
193 | terminated. |
177 | |
194 | |
178 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
195 | The remaining arguments are passed as arguments to the closure. |
179 | |
196 | |
180 | When the coroutine dies, the program will exit, just as in the main |
197 | See the C<Coro::State::new> constructor for info about the coro |
181 | program. |
198 | environment in which coro are executed. |
182 | |
199 | |
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200 | Calling C<exit> in a coro will do the same as calling exit outside |
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201 | the coro. Likewise, when the coro dies, the program will exit, |
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202 | just as it would in the main program. |
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203 | |
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204 | If you do not want that, you can provide a default C<die> handler, or |
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205 | simply avoid dieing (by use of C<eval>). |
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206 | |
183 | # create a new coroutine that just prints its arguments |
207 | Example: Create a new coro that just prints its arguments. |
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208 | |
184 | async { |
209 | async { |
185 | print "@_\n"; |
210 | print "@_\n"; |
186 | } 1,2,3,4; |
211 | } 1,2,3,4; |
187 | |
212 | |
188 | =cut |
213 | =item async_pool { ... } [@args...] |
189 | |
214 | |
190 | sub async(&@) { |
215 | Similar to C<async>, but uses a coro pool, so you should not call |
191 | my $pid = new Coro @_; |
216 | terminate or join on it (although you are allowed to), and you get a |
192 | $pid->ready; |
217 | coro that might have executed other code already (which can be good |
193 | $pid |
218 | or bad :). |
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219 | |
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220 | On the plus side, this function is about twice as fast as creating (and |
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221 | destroying) a completely new coro, so if you need a lot of generic |
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222 | coros in quick successsion, use C<async_pool>, not C<async>. |
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223 | |
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224 | The code block is executed in an C<eval> context and a warning will be |
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225 | issued in case of an exception instead of terminating the program, as |
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226 | C<async> does. As the coro is being reused, stuff like C<on_destroy> |
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227 | will not work in the expected way, unless you call terminate or cancel, |
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228 | which somehow defeats the purpose of pooling (but is fine in the |
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229 | exceptional case). |
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230 | |
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231 | The priority will be reset to C<0> after each run, tracing will be |
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232 | disabled, the description will be reset and the default output filehandle |
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233 | gets restored, so you can change all these. Otherwise the coro will |
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234 | be re-used "as-is": most notably if you change other per-coro global |
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235 | stuff such as C<$/> you I<must needs> revert that change, which is most |
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236 | simply done by using local as in: C<< local $/ >>. |
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237 | |
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238 | The idle pool size is limited to C<8> idle coros (this can be |
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239 | adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
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240 | coros as required. |
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241 | |
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242 | If you are concerned about pooled coros growing a lot because a |
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243 | single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
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244 | { terminate }> once per second or so to slowly replenish the pool. In |
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245 | addition to that, when the stacks used by a handler grows larger than 32kb |
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246 | (adjustable via $Coro::POOL_RSS) it will also be destroyed. |
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247 | |
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248 | =cut |
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249 | |
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250 | our $POOL_SIZE = 8; |
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251 | our $POOL_RSS = 32 * 1024; |
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252 | our @async_pool; |
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253 | |
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254 | sub pool_handler { |
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255 | while () { |
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256 | eval { |
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257 | &{&_pool_handler} while 1; |
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258 | }; |
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259 | |
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260 | warn $@ if $@; |
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261 | } |
194 | } |
262 | } |
195 | |
263 | |
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264 | =back |
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265 | |
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266 | =head1 STATIC METHODS |
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267 | |
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268 | Static methods are actually functions that implicitly operate on the |
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269 | current coro. |
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270 | |
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271 | =over 4 |
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272 | |
196 | =item schedule |
273 | =item schedule |
197 | |
274 | |
198 | Calls the scheduler. Please note that the current coroutine will not be put |
275 | Calls the scheduler. The scheduler will find the next coro that is |
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276 | to be run from the ready queue and switches to it. The next coro |
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277 | to be run is simply the one with the highest priority that is longest |
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278 | in its ready queue. If there is no coro ready, it will clal the |
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279 | C<$Coro::idle> hook. |
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280 | |
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281 | Please note that the current coro will I<not> be put into the ready |
199 | into the ready queue, so calling this function usually means you will |
282 | queue, so calling this function usually means you will never be called |
200 | never be called again unless something else (e.g. an event handler) calls |
283 | again unless something else (e.g. an event handler) calls C<< ->ready >>, |
201 | ready. |
284 | thus waking you up. |
202 | |
285 | |
203 | The canonical way to wait on external events is this: |
286 | This makes C<schedule> I<the> generic method to use to block the current |
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287 | coro and wait for events: first you remember the current coro in |
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288 | a variable, then arrange for some callback of yours to call C<< ->ready |
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289 | >> on that once some event happens, and last you call C<schedule> to put |
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290 | yourself to sleep. Note that a lot of things can wake your coro up, |
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291 | so you need to check whether the event indeed happened, e.g. by storing the |
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292 | status in a variable. |
204 | |
293 | |
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294 | See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
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295 | |
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296 | =item cede |
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297 | |
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298 | "Cede" to other coros. This function puts the current coro into |
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299 | the ready queue and calls C<schedule>, which has the effect of giving |
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300 | up the current "timeslice" to other coros of the same or higher |
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301 | priority. Once your coro gets its turn again it will automatically be |
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302 | resumed. |
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303 | |
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304 | This function is often called C<yield> in other languages. |
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305 | |
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306 | =item Coro::cede_notself |
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307 | |
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308 | Works like cede, but is not exported by default and will cede to I<any> |
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309 | coro, regardless of priority. This is useful sometimes to ensure |
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310 | progress is made. |
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311 | |
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312 | =item terminate [arg...] |
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313 | |
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314 | Terminates the current coro with the given status values (see L<cancel>). |
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315 | |
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316 | =item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
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317 | |
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318 | These function install enter and leave winders in the current scope. The |
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319 | enter block will be executed when on_enter is called and whenever the |
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320 | current coro is re-entered by the scheduler, while the leave block is |
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321 | executed whenever the current coro is blocked by the scheduler, and |
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322 | also when the containing scope is exited (by whatever means, be it exit, |
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323 | die, last etc.). |
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324 | |
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325 | I<Neither invoking the scheduler, nor exceptions, are allowed within those |
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326 | BLOCKs>. That means: do not even think about calling C<die> without an |
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327 | eval, and do not even think of entering the scheduler in any way. |
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328 | |
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329 | Since both BLOCKs are tied to the current scope, they will automatically |
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330 | be removed when the current scope exits. |
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331 | |
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332 | These functions implement the same concept as C<dynamic-wind> in scheme |
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333 | does, and are useful when you want to localise some resource to a specific |
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334 | coro. |
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335 | |
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336 | They slow down thread switching considerably for coros that use them |
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337 | (about 40% for a BLOCK with a single assignment, so thread switching is |
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338 | still reasonably fast if the handlers are fast). |
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339 | |
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340 | These functions are best understood by an example: The following function |
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341 | will change the current timezone to "Antarctica/South_Pole", which |
|
|
342 | requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
|
|
343 | which remember/change the current timezone and restore the previous |
|
|
344 | value, respectively, the timezone is only changed for the coro that |
|
|
345 | installed those handlers. |
|
|
346 | |
|
|
347 | use POSIX qw(tzset); |
|
|
348 | |
|
|
349 | async { |
|
|
350 | my $old_tz; # store outside TZ value here |
|
|
351 | |
|
|
352 | Coro::on_enter { |
|
|
353 | $old_tz = $ENV{TZ}; # remember the old value |
|
|
354 | |
|
|
355 | $ENV{TZ} = "Antarctica/South_Pole"; |
|
|
356 | tzset; # enable new value |
|
|
357 | }; |
|
|
358 | |
|
|
359 | Coro::on_leave { |
|
|
360 | $ENV{TZ} = $old_tz; |
|
|
361 | tzset; # restore old value |
|
|
362 | }; |
|
|
363 | |
|
|
364 | # at this place, the timezone is Antarctica/South_Pole, |
|
|
365 | # without disturbing the TZ of any other coro. |
|
|
366 | }; |
|
|
367 | |
|
|
368 | This can be used to localise about any resource (locale, uid, current |
|
|
369 | working directory etc.) to a block, despite the existance of other |
|
|
370 | coros. |
|
|
371 | |
|
|
372 | Another interesting example implements time-sliced multitasking using |
|
|
373 | interval timers (this could obviously be optimised, but does the job): |
|
|
374 | |
|
|
375 | # "timeslice" the given block |
|
|
376 | sub timeslice(&) { |
|
|
377 | use Time::HiRes (); |
|
|
378 | |
|
|
379 | Coro::on_enter { |
|
|
380 | # on entering the thread, we set an VTALRM handler to cede |
|
|
381 | $SIG{VTALRM} = sub { cede }; |
|
|
382 | # and then start the interval timer |
|
|
383 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
|
|
384 | }; |
|
|
385 | Coro::on_leave { |
|
|
386 | # on leaving the thread, we stop the interval timer again |
|
|
387 | Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
|
|
388 | }; |
|
|
389 | |
|
|
390 | &{+shift}; |
|
|
391 | } |
|
|
392 | |
|
|
393 | # use like this: |
|
|
394 | timeslice { |
|
|
395 | # The following is an endless loop that would normally |
|
|
396 | # monopolise the process. Since it runs in a timesliced |
|
|
397 | # environment, it will regularly cede to other threads. |
|
|
398 | while () { } |
|
|
399 | }; |
|
|
400 | |
|
|
401 | |
|
|
402 | =item killall |
|
|
403 | |
|
|
404 | Kills/terminates/cancels all coros except the currently running one. |
|
|
405 | |
|
|
406 | Note that while this will try to free some of the main interpreter |
|
|
407 | resources if the calling coro isn't the main coro, but one |
|
|
408 | cannot free all of them, so if a coro that is not the main coro |
|
|
409 | calls this function, there will be some one-time resource leak. |
|
|
410 | |
|
|
411 | =cut |
|
|
412 | |
|
|
413 | sub killall { |
|
|
414 | for (Coro::State::list) { |
|
|
415 | $_->cancel |
|
|
416 | if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
205 | { |
417 | } |
206 | # remember current coroutine |
418 | } |
|
|
419 | |
|
|
420 | =back |
|
|
421 | |
|
|
422 | =head1 CORO OBJECT METHODS |
|
|
423 | |
|
|
424 | These are the methods you can call on coro objects (or to create |
|
|
425 | them). |
|
|
426 | |
|
|
427 | =over 4 |
|
|
428 | |
|
|
429 | =item new Coro \&sub [, @args...] |
|
|
430 | |
|
|
431 | Create a new coro and return it. When the sub returns, the coro |
|
|
432 | automatically terminates as if C<terminate> with the returned values were |
|
|
433 | called. To make the coro run you must first put it into the ready |
|
|
434 | queue by calling the ready method. |
|
|
435 | |
|
|
436 | See C<async> and C<Coro::State::new> for additional info about the |
|
|
437 | coro environment. |
|
|
438 | |
|
|
439 | =cut |
|
|
440 | |
|
|
441 | sub _coro_run { |
|
|
442 | terminate &{+shift}; |
|
|
443 | } |
|
|
444 | |
|
|
445 | =item $success = $coro->ready |
|
|
446 | |
|
|
447 | Put the given coro into the end of its ready queue (there is one |
|
|
448 | queue for each priority) and return true. If the coro is already in |
|
|
449 | the ready queue, do nothing and return false. |
|
|
450 | |
|
|
451 | This ensures that the scheduler will resume this coro automatically |
|
|
452 | once all the coro of higher priority and all coro of the same |
|
|
453 | priority that were put into the ready queue earlier have been resumed. |
|
|
454 | |
|
|
455 | =item $coro->suspend |
|
|
456 | |
|
|
457 | Suspends the specified coro. A suspended coro works just like any other |
|
|
458 | coro, except that the scheduler will not select a suspended coro for |
|
|
459 | execution. |
|
|
460 | |
|
|
461 | Suspending a coro can be useful when you want to keep the coro from |
|
|
462 | running, but you don't want to destroy it, or when you want to temporarily |
|
|
463 | freeze a coro (e.g. for debugging) to resume it later. |
|
|
464 | |
|
|
465 | A scenario for the former would be to suspend all (other) coros after a |
|
|
466 | fork and keep them alive, so their destructors aren't called, but new |
|
|
467 | coros can be created. |
|
|
468 | |
|
|
469 | =item $coro->resume |
|
|
470 | |
|
|
471 | If the specified coro was suspended, it will be resumed. Note that when |
|
|
472 | the coro was in the ready queue when it was suspended, it might have been |
|
|
473 | unreadied by the scheduler, so an activation might have been lost. |
|
|
474 | |
|
|
475 | To avoid this, it is best to put a suspended coro into the ready queue |
|
|
476 | unconditionally, as every synchronisation mechanism must protect itself |
|
|
477 | against spurious wakeups, and the one in the Coro family certainly do |
|
|
478 | that. |
|
|
479 | |
|
|
480 | =item $is_ready = $coro->is_ready |
|
|
481 | |
|
|
482 | Returns true iff the Coro object is in the ready queue. Unless the Coro |
|
|
483 | object gets destroyed, it will eventually be scheduled by the scheduler. |
|
|
484 | |
|
|
485 | =item $is_running = $coro->is_running |
|
|
486 | |
|
|
487 | Returns true iff the Coro object is currently running. Only one Coro object |
|
|
488 | can ever be in the running state (but it currently is possible to have |
|
|
489 | multiple running Coro::States). |
|
|
490 | |
|
|
491 | =item $is_suspended = $coro->is_suspended |
|
|
492 | |
|
|
493 | Returns true iff this Coro object has been suspended. Suspended Coros will |
|
|
494 | not ever be scheduled. |
|
|
495 | |
|
|
496 | =item $coro->cancel (arg...) |
|
|
497 | |
|
|
498 | Terminates the given Coro and makes it return the given arguments as |
|
|
499 | status (default: the empty list). Never returns if the Coro is the |
|
|
500 | current Coro. |
|
|
501 | |
|
|
502 | =cut |
|
|
503 | |
|
|
504 | sub cancel { |
|
|
505 | my $self = shift; |
|
|
506 | |
|
|
507 | if ($current == $self) { |
|
|
508 | terminate @_; |
|
|
509 | } else { |
|
|
510 | $self->{_status} = [@_]; |
|
|
511 | Coro::State::cancel $self; |
|
|
512 | } |
|
|
513 | } |
|
|
514 | |
|
|
515 | =item $coro->schedule_to |
|
|
516 | |
|
|
517 | Puts the current coro to sleep (like C<Coro::schedule>), but instead |
|
|
518 | of continuing with the next coro from the ready queue, always switch to |
|
|
519 | the given coro object (regardless of priority etc.). The readyness |
|
|
520 | state of that coro isn't changed. |
|
|
521 | |
|
|
522 | This is an advanced method for special cases - I'd love to hear about any |
|
|
523 | uses for this one. |
|
|
524 | |
|
|
525 | =item $coro->cede_to |
|
|
526 | |
|
|
527 | Like C<schedule_to>, but puts the current coro into the ready |
|
|
528 | queue. This has the effect of temporarily switching to the given |
|
|
529 | coro, and continuing some time later. |
|
|
530 | |
|
|
531 | This is an advanced method for special cases - I'd love to hear about any |
|
|
532 | uses for this one. |
|
|
533 | |
|
|
534 | =item $coro->throw ([$scalar]) |
|
|
535 | |
|
|
536 | If C<$throw> is specified and defined, it will be thrown as an exception |
|
|
537 | inside the coro at the next convenient point in time. Otherwise |
|
|
538 | clears the exception object. |
|
|
539 | |
|
|
540 | Coro will check for the exception each time a schedule-like-function |
|
|
541 | returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
|
|
542 | >>, C<< Coro::Handle->readable >> and so on. Most of these functions |
|
|
543 | detect this case and return early in case an exception is pending. |
|
|
544 | |
|
|
545 | The exception object will be thrown "as is" with the specified scalar in |
|
|
546 | C<$@>, i.e. if it is a string, no line number or newline will be appended |
|
|
547 | (unlike with C<die>). |
|
|
548 | |
|
|
549 | This can be used as a softer means than C<cancel> to ask a coro to |
|
|
550 | end itself, although there is no guarantee that the exception will lead to |
|
|
551 | termination, and if the exception isn't caught it might well end the whole |
|
|
552 | program. |
|
|
553 | |
|
|
554 | You might also think of C<throw> as being the moral equivalent of |
|
|
555 | C<kill>ing a coro with a signal (in this case, a scalar). |
|
|
556 | |
|
|
557 | =item $coro->join |
|
|
558 | |
|
|
559 | Wait until the coro terminates and return any values given to the |
|
|
560 | C<terminate> or C<cancel> functions. C<join> can be called concurrently |
|
|
561 | from multiple coro, and all will be resumed and given the status |
|
|
562 | return once the C<$coro> terminates. |
|
|
563 | |
|
|
564 | =cut |
|
|
565 | |
|
|
566 | sub join { |
|
|
567 | my $self = shift; |
|
|
568 | |
|
|
569 | unless ($self->{_status}) { |
207 | my $current = $Coro::current; |
570 | my $current = $current; |
208 | |
571 | |
209 | # register a hypothetical event handler |
572 | push @{$self->{_on_destroy}}, sub { |
210 | on_event_invoke sub { |
|
|
211 | # wake up sleeping coroutine |
|
|
212 | $current->ready; |
573 | $current->ready; |
213 | undef $current; |
574 | undef $current; |
214 | }; |
575 | }; |
215 | |
576 | |
216 | # call schedule until event occured. |
|
|
217 | # in case we are woken up for other reasons |
|
|
218 | # (current still defined), loop. |
|
|
219 | Coro::schedule while $current; |
577 | &schedule while $current; |
220 | } |
578 | } |
221 | |
579 | |
222 | =item cede |
580 | wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
223 | |
|
|
224 | "Cede" to other coroutines. This function puts the current coroutine into the |
|
|
225 | ready queue and calls C<schedule>, which has the effect of giving up the |
|
|
226 | current "timeslice" to other coroutines of the same or higher priority. |
|
|
227 | |
|
|
228 | =item terminate [arg...] |
|
|
229 | |
|
|
230 | Terminates the current coroutine with the given status values (see L<cancel>). |
|
|
231 | |
|
|
232 | =cut |
|
|
233 | |
|
|
234 | sub terminate { |
|
|
235 | $current->cancel (@_); |
|
|
236 | } |
581 | } |
237 | |
582 | |
238 | =back |
583 | =item $coro->on_destroy (\&cb) |
239 | |
584 | |
240 | # dynamic methods |
585 | Registers a callback that is called when this coro gets destroyed, |
|
|
586 | but before it is joined. The callback gets passed the terminate arguments, |
|
|
587 | if any, and I<must not> die, under any circumstances. |
241 | |
588 | |
242 | =head2 COROUTINE METHODS |
|
|
243 | |
|
|
244 | These are the methods you can call on coroutine objects. |
|
|
245 | |
|
|
246 | =over 4 |
|
|
247 | |
|
|
248 | =item new Coro \&sub [, @args...] |
|
|
249 | |
|
|
250 | Create a new coroutine and return it. When the sub returns the coroutine |
|
|
251 | automatically terminates as if C<terminate> with the returned values were |
|
|
252 | called. To make the coroutine run you must first put it into the ready queue |
|
|
253 | by calling the ready method. |
|
|
254 | |
|
|
255 | Calling C<exit> in a coroutine will not work correctly, so do not do that. |
|
|
256 | |
|
|
257 | =cut |
589 | =cut |
258 | |
590 | |
259 | sub _run_coro { |
591 | sub on_destroy { |
260 | terminate &{+shift}; |
592 | my ($self, $cb) = @_; |
|
|
593 | |
|
|
594 | push @{ $self->{_on_destroy} }, $cb; |
261 | } |
595 | } |
262 | |
596 | |
263 | sub new { |
|
|
264 | my $class = shift; |
|
|
265 | |
|
|
266 | $class->SUPER::new (\&_run_coro, @_) |
|
|
267 | } |
|
|
268 | |
|
|
269 | =item $success = $coroutine->ready |
|
|
270 | |
|
|
271 | Put the given coroutine into the ready queue (according to it's priority) |
|
|
272 | and return true. If the coroutine is already in the ready queue, do nothing |
|
|
273 | and return false. |
|
|
274 | |
|
|
275 | =item $is_ready = $coroutine->is_ready |
|
|
276 | |
|
|
277 | Return wether the coroutine is currently the ready queue or not, |
|
|
278 | |
|
|
279 | =item $coroutine->cancel (arg...) |
|
|
280 | |
|
|
281 | Terminates the given coroutine and makes it return the given arguments as |
|
|
282 | status (default: the empty list). |
|
|
283 | |
|
|
284 | =cut |
|
|
285 | |
|
|
286 | sub cancel { |
|
|
287 | my $self = shift; |
|
|
288 | $self->{status} = [@_]; |
|
|
289 | push @destroy, $self; |
|
|
290 | $manager->ready; |
|
|
291 | &schedule if $current == $self; |
|
|
292 | } |
|
|
293 | |
|
|
294 | =item $coroutine->join |
|
|
295 | |
|
|
296 | Wait until the coroutine terminates and return any values given to the |
|
|
297 | C<terminate> or C<cancel> functions. C<join> can be called multiple times |
|
|
298 | from multiple coroutine. |
|
|
299 | |
|
|
300 | =cut |
|
|
301 | |
|
|
302 | sub join { |
|
|
303 | my $self = shift; |
|
|
304 | unless ($self->{status}) { |
|
|
305 | push @{$self->{join}}, $current; |
|
|
306 | &schedule; |
|
|
307 | } |
|
|
308 | wantarray ? @{$self->{status}} : $self->{status}[0]; |
|
|
309 | } |
|
|
310 | |
|
|
311 | =item $oldprio = $coroutine->prio ($newprio) |
597 | =item $oldprio = $coro->prio ($newprio) |
312 | |
598 | |
313 | Sets (or gets, if the argument is missing) the priority of the |
599 | Sets (or gets, if the argument is missing) the priority of the |
314 | coroutine. Higher priority coroutines get run before lower priority |
600 | coro. Higher priority coro get run before lower priority |
315 | coroutines. Priorities are small signed integers (currently -4 .. +3), |
601 | coro. Priorities are small signed integers (currently -4 .. +3), |
316 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
602 | that you can refer to using PRIO_xxx constants (use the import tag :prio |
317 | to get then): |
603 | to get then): |
318 | |
604 | |
319 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
605 | PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
320 | 3 > 1 > 0 > -1 > -3 > -4 |
606 | 3 > 1 > 0 > -1 > -3 > -4 |
321 | |
607 | |
322 | # set priority to HIGH |
608 | # set priority to HIGH |
323 | current->prio(PRIO_HIGH); |
609 | current->prio (PRIO_HIGH); |
324 | |
610 | |
325 | The idle coroutine ($Coro::idle) always has a lower priority than any |
611 | The idle coro ($Coro::idle) always has a lower priority than any |
326 | existing coroutine. |
612 | existing coro. |
327 | |
613 | |
328 | Changing the priority of the current coroutine will take effect immediately, |
614 | Changing the priority of the current coro will take effect immediately, |
329 | but changing the priority of coroutines in the ready queue (but not |
615 | but changing the priority of coro in the ready queue (but not |
330 | running) will only take effect after the next schedule (of that |
616 | running) will only take effect after the next schedule (of that |
331 | coroutine). This is a bug that will be fixed in some future version. |
617 | coro). This is a bug that will be fixed in some future version. |
332 | |
618 | |
333 | =item $newprio = $coroutine->nice ($change) |
619 | =item $newprio = $coro->nice ($change) |
334 | |
620 | |
335 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
621 | Similar to C<prio>, but subtract the given value from the priority (i.e. |
336 | higher values mean lower priority, just as in unix). |
622 | higher values mean lower priority, just as in unix). |
337 | |
623 | |
338 | =item $olddesc = $coroutine->desc ($newdesc) |
624 | =item $olddesc = $coro->desc ($newdesc) |
339 | |
625 | |
340 | Sets (or gets in case the argument is missing) the description for this |
626 | Sets (or gets in case the argument is missing) the description for this |
341 | coroutine. This is just a free-form string you can associate with a coroutine. |
627 | coro. This is just a free-form string you can associate with a |
|
|
628 | coro. |
|
|
629 | |
|
|
630 | This method simply sets the C<< $coro->{desc} >> member to the given |
|
|
631 | string. You can modify this member directly if you wish. |
342 | |
632 | |
343 | =cut |
633 | =cut |
344 | |
634 | |
345 | sub desc { |
635 | sub desc { |
346 | my $old = $_[0]{desc}; |
636 | my $old = $_[0]{desc}; |
347 | $_[0]{desc} = $_[1] if @_ > 1; |
637 | $_[0]{desc} = $_[1] if @_ > 1; |
348 | $old; |
638 | $old; |
349 | } |
639 | } |
350 | |
640 | |
|
|
641 | sub transfer { |
|
|
642 | require Carp; |
|
|
643 | Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
|
|
644 | } |
|
|
645 | |
351 | =back |
646 | =back |
352 | |
647 | |
353 | =head2 UTILITY FUNCTIONS |
648 | =head1 GLOBAL FUNCTIONS |
354 | |
649 | |
355 | =over 4 |
650 | =over 4 |
356 | |
651 | |
|
|
652 | =item Coro::nready |
|
|
653 | |
|
|
654 | Returns the number of coro that are currently in the ready state, |
|
|
655 | i.e. that can be switched to by calling C<schedule> directory or |
|
|
656 | indirectly. The value C<0> means that the only runnable coro is the |
|
|
657 | currently running one, so C<cede> would have no effect, and C<schedule> |
|
|
658 | would cause a deadlock unless there is an idle handler that wakes up some |
|
|
659 | coro. |
|
|
660 | |
|
|
661 | =item my $guard = Coro::guard { ... } |
|
|
662 | |
|
|
663 | This function still exists, but is deprecated. Please use the |
|
|
664 | C<Guard::guard> function instead. |
|
|
665 | |
|
|
666 | =cut |
|
|
667 | |
|
|
668 | BEGIN { *guard = \&Guard::guard } |
|
|
669 | |
357 | =item unblock_sub { ... } |
670 | =item unblock_sub { ... } |
358 | |
671 | |
359 | This utility function takes a BLOCK or code reference and "unblocks" it, |
672 | This utility function takes a BLOCK or code reference and "unblocks" it, |
360 | returning the new coderef. This means that the new coderef will return |
673 | returning a new coderef. Unblocking means that calling the new coderef |
361 | immediately without blocking, returning nothing, while the original code |
674 | will return immediately without blocking, returning nothing, while the |
362 | ref will be called (with parameters) from within its own coroutine. |
675 | original code ref will be called (with parameters) from within another |
|
|
676 | coro. |
363 | |
677 | |
364 | The reason this fucntion exists is that many event libraries (such as the |
678 | The reason this function exists is that many event libraries (such as the |
365 | venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
679 | venerable L<Event|Event> module) are not thread-safe (a weaker form |
366 | of thread-safety). This means you must not block within event callbacks, |
680 | of reentrancy). This means you must not block within event callbacks, |
367 | otherwise you might suffer from crashes or worse. |
681 | otherwise you might suffer from crashes or worse. The only event library |
|
|
682 | currently known that is safe to use without C<unblock_sub> is L<EV>. |
368 | |
683 | |
369 | This function allows your callbacks to block by executing them in another |
684 | This function allows your callbacks to block by executing them in another |
370 | coroutine where it is safe to block. One example where blocking is handy |
685 | coro where it is safe to block. One example where blocking is handy |
371 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
686 | is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
372 | disk. |
687 | disk, for example. |
373 | |
688 | |
374 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
689 | In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
375 | creating event callbacks that want to block. |
690 | creating event callbacks that want to block. |
376 | |
691 | |
377 | =cut |
692 | If your handler does not plan to block (e.g. simply sends a message to |
|
|
693 | another coro, or puts some other coro into the ready queue), there is |
|
|
694 | no reason to use C<unblock_sub>. |
378 | |
695 | |
379 | our @unblock_pool; |
696 | Note that you also need to use C<unblock_sub> for any other callbacks that |
|
|
697 | are indirectly executed by any C-based event loop. For example, when you |
|
|
698 | use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
|
|
699 | provides callbacks that are the result of some event callback, then you |
|
|
700 | must not block either, or use C<unblock_sub>. |
|
|
701 | |
|
|
702 | =cut |
|
|
703 | |
380 | our @unblock_queue; |
704 | our @unblock_queue; |
381 | our $UNBLOCK_POOL_SIZE = 2; |
|
|
382 | |
705 | |
383 | sub unblock_handler_ { |
706 | # we create a special coro because we want to cede, |
384 | while () { |
707 | # to reduce pressure on the coro pool (because most callbacks |
385 | my ($cb, @arg) = @{ delete $Coro::current->{arg} }; |
708 | # return immediately and can be reused) and because we cannot cede |
386 | $cb->(@arg); |
709 | # inside an event callback. |
387 | |
|
|
388 | last if @unblock_pool >= $UNBLOCK_POOL_SIZE; |
|
|
389 | push @unblock_pool, $Coro::current; |
|
|
390 | schedule; |
|
|
391 | } |
|
|
392 | } |
|
|
393 | |
|
|
394 | our $unblock_scheduler = async { |
710 | our $unblock_scheduler = new Coro sub { |
395 | while () { |
711 | while () { |
396 | while (my $cb = pop @unblock_queue) { |
712 | while (my $cb = pop @unblock_queue) { |
397 | my $handler = (pop @unblock_pool or new Coro \&unblock_handler_); |
713 | &async_pool (@$cb); |
398 | $handler->{arg} = $cb; |
714 | |
399 | $handler->ready; |
715 | # for short-lived callbacks, this reduces pressure on the coro pool |
|
|
716 | # as the chance is very high that the async_poll coro will be back |
|
|
717 | # in the idle state when cede returns |
400 | cede; |
718 | cede; |
401 | } |
719 | } |
402 | |
720 | schedule; # sleep well |
403 | schedule; |
|
|
404 | } |
721 | } |
405 | }; |
722 | }; |
|
|
723 | $unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
406 | |
724 | |
407 | sub unblock_sub(&) { |
725 | sub unblock_sub(&) { |
408 | my $cb = shift; |
726 | my $cb = shift; |
409 | |
727 | |
410 | sub { |
728 | sub { |
411 | push @unblock_queue, [$cb, @_]; |
729 | unshift @unblock_queue, [$cb, @_]; |
412 | $unblock_scheduler->ready; |
730 | $unblock_scheduler->ready; |
413 | } |
731 | } |
414 | } |
732 | } |
415 | |
733 | |
|
|
734 | =item $cb = Coro::rouse_cb |
|
|
735 | |
|
|
736 | Create and return a "rouse callback". That's a code reference that, |
|
|
737 | when called, will remember a copy of its arguments and notify the owner |
|
|
738 | coro of the callback. |
|
|
739 | |
|
|
740 | See the next function. |
|
|
741 | |
|
|
742 | =item @args = Coro::rouse_wait [$cb] |
|
|
743 | |
|
|
744 | Wait for the specified rouse callback (or the last one that was created in |
|
|
745 | this coro). |
|
|
746 | |
|
|
747 | As soon as the callback is invoked (or when the callback was invoked |
|
|
748 | before C<rouse_wait>), it will return the arguments originally passed to |
|
|
749 | the rouse callback. In scalar context, that means you get the I<last> |
|
|
750 | argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
|
|
751 | statement at the end. |
|
|
752 | |
|
|
753 | See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
|
|
754 | |
416 | =back |
755 | =back |
417 | |
756 | |
418 | =cut |
757 | =cut |
419 | |
758 | |
420 | 1; |
759 | 1; |
421 | |
760 | |
|
|
761 | =head1 HOW TO WAIT FOR A CALLBACK |
|
|
762 | |
|
|
763 | It is very common for a coro to wait for some callback to be |
|
|
764 | called. This occurs naturally when you use coro in an otherwise |
|
|
765 | event-based program, or when you use event-based libraries. |
|
|
766 | |
|
|
767 | These typically register a callback for some event, and call that callback |
|
|
768 | when the event occured. In a coro, however, you typically want to |
|
|
769 | just wait for the event, simplyifying things. |
|
|
770 | |
|
|
771 | For example C<< AnyEvent->child >> registers a callback to be called when |
|
|
772 | a specific child has exited: |
|
|
773 | |
|
|
774 | my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
|
|
775 | |
|
|
776 | But from within a coro, you often just want to write this: |
|
|
777 | |
|
|
778 | my $status = wait_for_child $pid; |
|
|
779 | |
|
|
780 | Coro offers two functions specifically designed to make this easy, |
|
|
781 | C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
|
|
782 | |
|
|
783 | The first function, C<rouse_cb>, generates and returns a callback that, |
|
|
784 | when invoked, will save its arguments and notify the coro that |
|
|
785 | created the callback. |
|
|
786 | |
|
|
787 | The second function, C<rouse_wait>, waits for the callback to be called |
|
|
788 | (by calling C<schedule> to go to sleep) and returns the arguments |
|
|
789 | originally passed to the callback. |
|
|
790 | |
|
|
791 | Using these functions, it becomes easy to write the C<wait_for_child> |
|
|
792 | function mentioned above: |
|
|
793 | |
|
|
794 | sub wait_for_child($) { |
|
|
795 | my ($pid) = @_; |
|
|
796 | |
|
|
797 | my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
|
|
798 | |
|
|
799 | my ($rpid, $rstatus) = Coro::rouse_wait; |
|
|
800 | $rstatus |
|
|
801 | } |
|
|
802 | |
|
|
803 | In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
|
|
804 | you can roll your own, using C<schedule>: |
|
|
805 | |
|
|
806 | sub wait_for_child($) { |
|
|
807 | my ($pid) = @_; |
|
|
808 | |
|
|
809 | # store the current coro in $current, |
|
|
810 | # and provide result variables for the closure passed to ->child |
|
|
811 | my $current = $Coro::current; |
|
|
812 | my ($done, $rstatus); |
|
|
813 | |
|
|
814 | # pass a closure to ->child |
|
|
815 | my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
|
|
816 | $rstatus = $_[1]; # remember rstatus |
|
|
817 | $done = 1; # mark $rstatus as valud |
|
|
818 | }); |
|
|
819 | |
|
|
820 | # wait until the closure has been called |
|
|
821 | schedule while !$done; |
|
|
822 | |
|
|
823 | $rstatus |
|
|
824 | } |
|
|
825 | |
|
|
826 | |
422 | =head1 BUGS/LIMITATIONS |
827 | =head1 BUGS/LIMITATIONS |
423 | |
828 | |
424 | - you must make very sure that no coro is still active on global |
829 | =over 4 |
425 | destruction. very bad things might happen otherwise (usually segfaults). |
|
|
426 | |
830 | |
|
|
831 | =item fork with pthread backend |
|
|
832 | |
|
|
833 | When Coro is compiled using the pthread backend (which isn't recommended |
|
|
834 | but required on many BSDs as their libcs are completely broken), then |
|
|
835 | coro will not survive a fork. There is no known workaround except to |
|
|
836 | fix your libc and use a saner backend. |
|
|
837 | |
|
|
838 | =item perl process emulation ("threads") |
|
|
839 | |
427 | - this module is not thread-safe. You should only ever use this module |
840 | This module is not perl-pseudo-thread-safe. You should only ever use this |
428 | from the same thread (this requirement might be losened in the future |
841 | module from the first thread (this requirement might be removed in the |
429 | to allow per-thread schedulers, but Coro::State does not yet allow |
842 | future to allow per-thread schedulers, but Coro::State does not yet allow |
430 | this). |
843 | this). I recommend disabling thread support and using processes, as having |
|
|
844 | the windows process emulation enabled under unix roughly halves perl |
|
|
845 | performance, even when not used. |
|
|
846 | |
|
|
847 | =item coro switching is not signal safe |
|
|
848 | |
|
|
849 | You must not switch to another coro from within a signal handler |
|
|
850 | (only relevant with %SIG - most event libraries provide safe signals). |
|
|
851 | |
|
|
852 | That means you I<MUST NOT> call any function that might "block" the |
|
|
853 | current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
|
|
854 | anything that calls those. Everything else, including calling C<ready>, |
|
|
855 | works. |
|
|
856 | |
|
|
857 | =back |
|
|
858 | |
|
|
859 | |
|
|
860 | =head1 WINDOWS PROCESS EMULATION |
|
|
861 | |
|
|
862 | A great many people seem to be confused about ithreads (for example, Chip |
|
|
863 | Salzenberg called me unintelligent, incapable, stupid and gullible, |
|
|
864 | while in the same mail making rather confused statements about perl |
|
|
865 | ithreads (for example, that memory or files would be shared), showing his |
|
|
866 | lack of understanding of this area - if it is hard to understand for Chip, |
|
|
867 | it is probably not obvious to everybody). |
|
|
868 | |
|
|
869 | What follows is an ultra-condensed version of my talk about threads in |
|
|
870 | scripting languages given onthe perl workshop 2009: |
|
|
871 | |
|
|
872 | The so-called "ithreads" were originally implemented for two reasons: |
|
|
873 | first, to (badly) emulate unix processes on native win32 perls, and |
|
|
874 | secondly, to replace the older, real thread model ("5.005-threads"). |
|
|
875 | |
|
|
876 | It does that by using threads instead of OS processes. The difference |
|
|
877 | between processes and threads is that threads share memory (and other |
|
|
878 | state, such as files) between threads within a single process, while |
|
|
879 | processes do not share anything (at least not semantically). That |
|
|
880 | means that modifications done by one thread are seen by others, while |
|
|
881 | modifications by one process are not seen by other processes. |
|
|
882 | |
|
|
883 | The "ithreads" work exactly like that: when creating a new ithreads |
|
|
884 | process, all state is copied (memory is copied physically, files and code |
|
|
885 | is copied logically). Afterwards, it isolates all modifications. On UNIX, |
|
|
886 | the same behaviour can be achieved by using operating system processes, |
|
|
887 | except that UNIX typically uses hardware built into the system to do this |
|
|
888 | efficiently, while the windows process emulation emulates this hardware in |
|
|
889 | software (rather efficiently, but of course it is still much slower than |
|
|
890 | dedicated hardware). |
|
|
891 | |
|
|
892 | As mentioned before, loading code, modifying code, modifying data |
|
|
893 | structures and so on is only visible in the ithreads process doing the |
|
|
894 | modification, not in other ithread processes within the same OS process. |
|
|
895 | |
|
|
896 | This is why "ithreads" do not implement threads for perl at all, only |
|
|
897 | processes. What makes it so bad is that on non-windows platforms, you can |
|
|
898 | actually take advantage of custom hardware for this purpose (as evidenced |
|
|
899 | by the forks module, which gives you the (i-) threads API, just much |
|
|
900 | faster). |
|
|
901 | |
|
|
902 | Sharing data is in the i-threads model is done by transfering data |
|
|
903 | structures between threads using copying semantics, which is very slow - |
|
|
904 | shared data simply does not exist. Benchmarks using i-threads which are |
|
|
905 | communication-intensive show extremely bad behaviour with i-threads (in |
|
|
906 | fact, so bad that Coro, which cannot take direct advantage of multiple |
|
|
907 | CPUs, is often orders of magnitude faster because it shares data using |
|
|
908 | real threads, refer to my talk for details). |
|
|
909 | |
|
|
910 | As summary, i-threads *use* threads to implement processes, while |
|
|
911 | the compatible forks module *uses* processes to emulate, uhm, |
|
|
912 | processes. I-threads slow down every perl program when enabled, and |
|
|
913 | outside of windows, serve no (or little) practical purpose, but |
|
|
914 | disadvantages every single-threaded Perl program. |
|
|
915 | |
|
|
916 | This is the reason that I try to avoid the name "ithreads", as it is |
|
|
917 | misleading as it implies that it implements some kind of thread model for |
|
|
918 | perl, and prefer the name "windows process emulation", which describes the |
|
|
919 | actual use and behaviour of it much better. |
431 | |
920 | |
432 | =head1 SEE ALSO |
921 | =head1 SEE ALSO |
433 | |
922 | |
|
|
923 | Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
|
|
924 | |
|
|
925 | Debugging: L<Coro::Debug>. |
|
|
926 | |
434 | Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>. |
927 | Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
435 | |
928 | |
436 | Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
929 | Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
|
|
930 | L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
437 | |
931 | |
438 | Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>. |
932 | I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
439 | |
933 | |
440 | Embedding: L<Coro:MakeMaker> |
934 | Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
|
|
935 | a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
|
|
936 | L<Coro::Select>. |
|
|
937 | |
|
|
938 | XS API: L<Coro::MakeMaker>. |
|
|
939 | |
|
|
940 | Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
441 | |
941 | |
442 | =head1 AUTHOR |
942 | =head1 AUTHOR |
443 | |
943 | |
444 | Marc Lehmann <schmorp@schmorp.de> |
944 | Marc Lehmann <schmorp@schmorp.de> |
445 | http://home.schmorp.de/ |
945 | http://home.schmorp.de/ |