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