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=head1 NAME |
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Coro - the only real threads in perl |
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=head1 SYNOPSIS |
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use Coro; |
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async { |
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# some asynchronous thread of execution |
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print "2\n"; |
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cede; # yield back to main |
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print "4\n"; |
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}; |
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print "1\n"; |
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cede; # yield to coroutine |
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print "3\n"; |
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cede; # and again |
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# use locking |
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use Coro::Semaphore; |
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my $lock = new Coro::Semaphore; |
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my $locked; |
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$lock->down; |
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$locked = 1; |
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$lock->up; |
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=head1 DESCRIPTION |
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For a tutorial-style introduction, please read the L<Coro::Intro> |
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manpage. This manpage mainly contains reference information. |
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This module collection manages continuations in general, most often |
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in the form of cooperative threads (also called coroutines in the |
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documentation). They are similar to kernel threads but don't (in general) |
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run in parallel at the same time even on SMP machines. The specific flavor |
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of thread offered by this module also guarantees you that it will not |
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switch between threads unless necessary, at easily-identified points in |
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your program, so locking and parallel access are rarely an issue, making |
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thread programming much safer and easier than using other thread models. |
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Unlike the so-called "Perl threads" (which are not actually real threads |
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but only the windows process emulation ported to unix), Coro provides a |
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full shared address space, which makes communication between threads |
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very easy. And threads are fast, too: disabling the Windows process |
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emulation code in your perl and using Coro can easily result in a two to |
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four times speed increase for your programs. |
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Coro achieves that by supporting multiple running interpreters that share |
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data, which is especially useful to code pseudo-parallel processes and |
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for event-based programming, such as multiple HTTP-GET requests running |
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concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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into an event-based environment. |
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In this module, a thread is defined as "callchain + lexical variables + |
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@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain, |
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its own set of lexicals and its own set of perls most important global |
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variables (see L<Coro::State> for more configuration and background info). |
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|
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See also the C<SEE ALSO> section at the end of this document - the Coro |
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module family is quite large. |
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=cut |
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package Coro; |
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use strict qw(vars subs); |
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no warnings "uninitialized"; |
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use Guard (); |
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use Coro::State; |
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use base qw(Coro::State Exporter); |
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|
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our $idle; # idle handler |
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our $main; # main coroutine |
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our $current; # current coroutine |
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|
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our $VERSION = 5.13; |
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our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
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our %EXPORT_TAGS = ( |
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prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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); |
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our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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|
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=head1 GLOBAL VARIABLES |
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=over 4 |
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=item $Coro::main |
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|
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This variable stores the coroutine object that represents the main |
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program. While you cna C<ready> it and do most other things you can do to |
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coroutines, it is mainly useful to compare again C<$Coro::current>, to see |
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whether you are running in the main program or not. |
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|
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=cut |
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# $main is now being initialised by Coro::State |
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|
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=item $Coro::current |
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|
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The coroutine object representing the current coroutine (the last |
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coroutine that the Coro scheduler switched to). The initial value is |
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C<$Coro::main> (of course). |
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This variable is B<strictly> I<read-only>. You can take copies of the |
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value stored in it and use it as any other coroutine object, but you must |
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not otherwise modify the variable itself. |
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|
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=cut |
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sub current() { $current } # [DEPRECATED] |
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|
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=item $Coro::idle |
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|
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This variable is mainly useful to integrate Coro into event loops. It is |
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usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
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pretty low-level functionality. |
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This variable stores either a coroutine or a callback. |
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If it is a callback, the it is called whenever the scheduler finds no |
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ready coroutines to run. The default implementation prints "FATAL: |
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deadlock detected" and exits, because the program has no other way to |
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continue. |
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If it is a coroutine object, then this object will be readied (without |
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invoking any ready hooks, however) when the scheduler finds no other ready |
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coroutines to run. |
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This hook is overwritten by modules such as C<Coro::EV> and |
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C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
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coroutine so the scheduler can run it. |
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Note that the callback I<must not>, under any circumstances, block |
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the current coroutine. Normally, this is achieved by having an "idle |
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coroutine" that calls the event loop and then blocks again, and then |
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readying that coroutine in the idle handler, or by simply placing the idle |
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coroutine in this variable. |
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See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
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technique. |
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Please note that if your callback recursively invokes perl (e.g. for event |
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handlers), then it must be prepared to be called recursively itself. |
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|
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=cut |
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$idle = sub { |
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require Carp; |
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Carp::croak ("FATAL: deadlock detected"); |
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}; |
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|
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# this coroutine is necessary because a coroutine |
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# cannot destroy itself. |
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our @destroy; |
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our $manager; |
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$manager = new Coro sub { |
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while () { |
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Coro::_cancel shift @destroy |
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while @destroy; |
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&schedule; |
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} |
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}; |
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$manager->{desc} = "[coro manager]"; |
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$manager->prio (PRIO_MAX); |
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=back |
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|
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=head1 SIMPLE COROUTINE CREATION |
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=over 4 |
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=item async { ... } [@args...] |
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|
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Create a new coroutine and return its coroutine object (usually |
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unused). The coroutine will be put into the ready queue, so |
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it will start running automatically on the next scheduler run. |
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The first argument is a codeblock/closure that should be executed in the |
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coroutine. When it returns argument returns the coroutine is automatically |
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terminated. |
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The remaining arguments are passed as arguments to the closure. |
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See the C<Coro::State::new> constructor for info about the coroutine |
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environment in which coroutines are executed. |
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|
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Calling C<exit> in a coroutine will do the same as calling exit outside |
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the coroutine. Likewise, when the coroutine dies, the program will exit, |
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just as it would in the main program. |
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|
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If you do not want that, you can provide a default C<die> handler, or |
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simply avoid dieing (by use of C<eval>). |
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Example: Create a new coroutine that just prints its arguments. |
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async { |
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print "@_\n"; |
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} 1,2,3,4; |
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=cut |
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sub async(&@) { |
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my $coro = new Coro @_; |
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$coro->ready; |
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$coro |
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} |
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=item async_pool { ... } [@args...] |
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Similar to C<async>, but uses a coroutine pool, so you should not call |
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terminate or join on it (although you are allowed to), and you get a |
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coroutine that might have executed other code already (which can be good |
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or bad :). |
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On the plus side, this function is about twice as fast as creating (and |
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destroying) a completely new coroutine, so if you need a lot of generic |
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coroutines in quick successsion, use C<async_pool>, not C<async>. |
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The code block is executed in an C<eval> context and a warning will be |
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issued in case of an exception instead of terminating the program, as |
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C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
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will not work in the expected way, unless you call terminate or cancel, |
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which somehow defeats the purpose of pooling (but is fine in the |
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exceptional case). |
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The priority will be reset to C<0> after each run, tracing will be |
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disabled, the description will be reset and the default output filehandle |
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gets restored, so you can change all these. Otherwise the coroutine will |
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be re-used "as-is": most notably if you change other per-coroutine global |
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stuff such as C<$/> you I<must needs> revert that change, which is most |
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simply done by using local as in: C<< local $/ >>. |
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|
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The idle pool size is limited to C<8> idle coroutines (this can be |
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adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
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coros as required. |
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|
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If you are concerned about pooled coroutines growing a lot because a |
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single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
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{ terminate }> once per second or so to slowly replenish the pool. In |
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addition to that, when the stacks used by a handler grows larger than 32kb |
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(adjustable via $Coro::POOL_RSS) it will also be destroyed. |
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|
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=cut |
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our $POOL_SIZE = 8; |
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our $POOL_RSS = 32 * 1024; |
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our @async_pool; |
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|
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sub pool_handler { |
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while () { |
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eval { |
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&{&_pool_handler} while 1; |
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}; |
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|
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warn $@ if $@; |
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} |
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} |
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|
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=back |
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=head1 STATIC METHODS |
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|
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Static methods are actually functions that implicitly operate on the |
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current coroutine. |
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|
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=over 4 |
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=item schedule |
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|
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Calls the scheduler. The scheduler will find the next coroutine that is |
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to be run from the ready queue and switches to it. The next coroutine |
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to be run is simply the one with the highest priority that is longest |
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in its ready queue. If there is no coroutine ready, it will clal the |
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C<$Coro::idle> hook. |
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Please note that the current coroutine will I<not> be put into the ready |
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queue, so calling this function usually means you will never be called |
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again unless something else (e.g. an event handler) calls C<< ->ready >>, |
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thus waking you up. |
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This makes C<schedule> I<the> generic method to use to block the current |
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coroutine and wait for events: first you remember the current coroutine in |
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a variable, then arrange for some callback of yours to call C<< ->ready |
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>> on that once some event happens, and last you call C<schedule> to put |
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yourself to sleep. Note that a lot of things can wake your coroutine up, |
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so you need to check whether the event indeed happened, e.g. by storing the |
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status in a variable. |
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|
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See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
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|
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=item cede |
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|
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"Cede" to other coroutines. This function puts the current coroutine into |
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the ready queue and calls C<schedule>, which has the effect of giving |
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up the current "timeslice" to other coroutines of the same or higher |
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priority. Once your coroutine gets its turn again it will automatically be |
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resumed. |
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|
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This function is often called C<yield> in other languages. |
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|
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=item Coro::cede_notself |
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Works like cede, but is not exported by default and will cede to I<any> |
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coroutine, regardless of priority. This is useful sometimes to ensure |
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progress is made. |
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1.102 |
|
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1.40 |
=item terminate [arg...] |
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1.7 |
|
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Terminates the current coroutine with the given status values (see L<cancel>). |
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1.13 |
|
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=item Coro::on_enter BLOCK, Coro::on_leave BLOCK |
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These function install enter and leave winders in the current scope. The |
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enter block will be executed when on_enter is called and whenever the |
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current coroutine is re-entered by the scheduler, while the leave block is |
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executed whenever the current coroutine is blocked by the scheduler, and |
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also when the containing scope is exited (by whatever means, be it exit, |
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die, last etc.). |
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I<Neither invoking the scheduler, nor exceptions, are allowed within those |
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BLOCKs>. That means: do not even think about calling C<die> without an |
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eval, and do not even think of entering the scheduler in any way. |
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Since both BLOCKs are tied to the current scope, they will automatically |
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be removed when the current scope exits. |
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These functions implement the same concept as C<dynamic-wind> in scheme |
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does, and are useful when you want to localise some resource to a specific |
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coroutine. |
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|
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They slow down coroutine switching considerably for coroutines that use |
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them (But coroutine switching is still reasonably fast if the handlers are |
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fast). |
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These functions are best understood by an example: The following function |
344 |
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will change the current timezone to "Antarctica/South_Pole", which |
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requires a call to C<tzset>, but by using C<on_enter> and C<on_leave>, |
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which remember/change the current timezone and restore the previous |
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value, respectively, the timezone is only changes for the coroutine that |
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installed those handlers. |
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|
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use POSIX qw(tzset); |
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async { |
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my $old_tz; # store outside TZ value here |
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Coro::on_enter { |
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|
|
$old_tz = $ENV{TZ}; # remember the old value |
357 |
|
|
|
358 |
|
|
$ENV{TZ} = "Antarctica/South_Pole"; |
359 |
|
|
tzset; # enable new value |
360 |
|
|
}; |
361 |
|
|
|
362 |
|
|
Coro::on_leave { |
363 |
|
|
$ENV{TZ} = $old_tz; |
364 |
|
|
tzset; # restore old value |
365 |
|
|
}; |
366 |
|
|
|
367 |
|
|
# at this place, the timezone is Antarctica/South_Pole, |
368 |
|
|
# without disturbing the TZ of any other coroutine. |
369 |
|
|
}; |
370 |
|
|
|
371 |
|
|
This can be used to localise about any resource (locale, uid, current |
372 |
|
|
working directory etc.) to a block, despite the existance of other |
373 |
|
|
coroutines. |
374 |
|
|
|
375 |
root |
1.141 |
=item killall |
376 |
|
|
|
377 |
root |
1.247 |
Kills/terminates/cancels all coroutines except the currently running one. |
378 |
|
|
|
379 |
|
|
Note that while this will try to free some of the main interpreter |
380 |
|
|
resources if the calling coroutine isn't the main coroutine, but one |
381 |
|
|
cannot free all of them, so if a coroutine that is not the main coroutine |
382 |
|
|
calls this function, there will be some one-time resource leak. |
383 |
root |
1.181 |
|
384 |
root |
1.1 |
=cut |
385 |
|
|
|
386 |
root |
1.141 |
sub killall { |
387 |
|
|
for (Coro::State::list) { |
388 |
|
|
$_->cancel |
389 |
|
|
if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
390 |
|
|
} |
391 |
|
|
} |
392 |
|
|
|
393 |
root |
1.8 |
=back |
394 |
|
|
|
395 |
root |
1.234 |
=head1 COROUTINE OBJECT METHODS |
396 |
root |
1.8 |
|
397 |
root |
1.181 |
These are the methods you can call on coroutine objects (or to create |
398 |
|
|
them). |
399 |
root |
1.6 |
|
400 |
root |
1.8 |
=over 4 |
401 |
|
|
|
402 |
root |
1.13 |
=item new Coro \&sub [, @args...] |
403 |
root |
1.8 |
|
404 |
root |
1.181 |
Create a new coroutine and return it. When the sub returns, the coroutine |
405 |
root |
1.40 |
automatically terminates as if C<terminate> with the returned values were |
406 |
root |
1.181 |
called. To make the coroutine run you must first put it into the ready |
407 |
|
|
queue by calling the ready method. |
408 |
root |
1.13 |
|
409 |
root |
1.145 |
See C<async> and C<Coro::State::new> for additional info about the |
410 |
|
|
coroutine environment. |
411 |
root |
1.89 |
|
412 |
root |
1.6 |
=cut |
413 |
|
|
|
414 |
root |
1.241 |
sub _coro_run { |
415 |
root |
1.13 |
terminate &{+shift}; |
416 |
|
|
} |
417 |
|
|
|
418 |
root |
1.92 |
=item $success = $coroutine->ready |
419 |
root |
1.1 |
|
420 |
root |
1.181 |
Put the given coroutine into the end of its ready queue (there is one |
421 |
|
|
queue for each priority) and return true. If the coroutine is already in |
422 |
|
|
the ready queue, do nothing and return false. |
423 |
|
|
|
424 |
|
|
This ensures that the scheduler will resume this coroutine automatically |
425 |
|
|
once all the coroutines of higher priority and all coroutines of the same |
426 |
|
|
priority that were put into the ready queue earlier have been resumed. |
427 |
root |
1.1 |
|
428 |
root |
1.92 |
=item $is_ready = $coroutine->is_ready |
429 |
root |
1.90 |
|
430 |
root |
1.196 |
Return whether the coroutine is currently the ready queue or not, |
431 |
root |
1.28 |
|
432 |
root |
1.92 |
=item $coroutine->cancel (arg...) |
433 |
root |
1.28 |
|
434 |
root |
1.92 |
Terminates the given coroutine and makes it return the given arguments as |
435 |
root |
1.103 |
status (default: the empty list). Never returns if the coroutine is the |
436 |
|
|
current coroutine. |
437 |
root |
1.28 |
|
438 |
|
|
=cut |
439 |
|
|
|
440 |
|
|
sub cancel { |
441 |
pcg |
1.59 |
my $self = shift; |
442 |
root |
1.103 |
|
443 |
|
|
if ($current == $self) { |
444 |
root |
1.226 |
terminate @_; |
445 |
root |
1.103 |
} else { |
446 |
root |
1.226 |
$self->{_status} = [@_]; |
447 |
root |
1.103 |
$self->_cancel; |
448 |
|
|
} |
449 |
root |
1.40 |
} |
450 |
|
|
|
451 |
root |
1.229 |
=item $coroutine->schedule_to |
452 |
|
|
|
453 |
|
|
Puts the current coroutine to sleep (like C<Coro::schedule>), but instead |
454 |
|
|
of continuing with the next coro from the ready queue, always switch to |
455 |
|
|
the given coroutine object (regardless of priority etc.). The readyness |
456 |
|
|
state of that coroutine isn't changed. |
457 |
|
|
|
458 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
459 |
|
|
uses for this one. |
460 |
|
|
|
461 |
|
|
=item $coroutine->cede_to |
462 |
|
|
|
463 |
|
|
Like C<schedule_to>, but puts the current coroutine into the ready |
464 |
|
|
queue. This has the effect of temporarily switching to the given |
465 |
|
|
coroutine, and continuing some time later. |
466 |
|
|
|
467 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
468 |
|
|
uses for this one. |
469 |
|
|
|
470 |
root |
1.208 |
=item $coroutine->throw ([$scalar]) |
471 |
|
|
|
472 |
|
|
If C<$throw> is specified and defined, it will be thrown as an exception |
473 |
root |
1.222 |
inside the coroutine at the next convenient point in time. Otherwise |
474 |
|
|
clears the exception object. |
475 |
|
|
|
476 |
|
|
Coro will check for the exception each time a schedule-like-function |
477 |
|
|
returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
478 |
root |
1.223 |
>>, C<< Coro::Handle->readable >> and so on. Most of these functions |
479 |
|
|
detect this case and return early in case an exception is pending. |
480 |
root |
1.208 |
|
481 |
|
|
The exception object will be thrown "as is" with the specified scalar in |
482 |
|
|
C<$@>, i.e. if it is a string, no line number or newline will be appended |
483 |
|
|
(unlike with C<die>). |
484 |
|
|
|
485 |
|
|
This can be used as a softer means than C<cancel> to ask a coroutine to |
486 |
|
|
end itself, although there is no guarantee that the exception will lead to |
487 |
|
|
termination, and if the exception isn't caught it might well end the whole |
488 |
|
|
program. |
489 |
|
|
|
490 |
|
|
You might also think of C<throw> as being the moral equivalent of |
491 |
|
|
C<kill>ing a coroutine with a signal (in this case, a scalar). |
492 |
|
|
|
493 |
root |
1.92 |
=item $coroutine->join |
494 |
root |
1.40 |
|
495 |
|
|
Wait until the coroutine terminates and return any values given to the |
496 |
root |
1.143 |
C<terminate> or C<cancel> functions. C<join> can be called concurrently |
497 |
root |
1.181 |
from multiple coroutines, and all will be resumed and given the status |
498 |
|
|
return once the C<$coroutine> terminates. |
499 |
root |
1.40 |
|
500 |
|
|
=cut |
501 |
|
|
|
502 |
|
|
sub join { |
503 |
|
|
my $self = shift; |
504 |
root |
1.103 |
|
505 |
root |
1.142 |
unless ($self->{_status}) { |
506 |
root |
1.103 |
my $current = $current; |
507 |
|
|
|
508 |
root |
1.142 |
push @{$self->{_on_destroy}}, sub { |
509 |
root |
1.103 |
$current->ready; |
510 |
|
|
undef $current; |
511 |
|
|
}; |
512 |
|
|
|
513 |
|
|
&schedule while $current; |
514 |
root |
1.40 |
} |
515 |
root |
1.103 |
|
516 |
root |
1.142 |
wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
517 |
root |
1.31 |
} |
518 |
|
|
|
519 |
root |
1.101 |
=item $coroutine->on_destroy (\&cb) |
520 |
|
|
|
521 |
|
|
Registers a callback that is called when this coroutine gets destroyed, |
522 |
|
|
but before it is joined. The callback gets passed the terminate arguments, |
523 |
root |
1.181 |
if any, and I<must not> die, under any circumstances. |
524 |
root |
1.101 |
|
525 |
|
|
=cut |
526 |
|
|
|
527 |
|
|
sub on_destroy { |
528 |
|
|
my ($self, $cb) = @_; |
529 |
|
|
|
530 |
root |
1.142 |
push @{ $self->{_on_destroy} }, $cb; |
531 |
root |
1.101 |
} |
532 |
|
|
|
533 |
root |
1.92 |
=item $oldprio = $coroutine->prio ($newprio) |
534 |
root |
1.31 |
|
535 |
root |
1.41 |
Sets (or gets, if the argument is missing) the priority of the |
536 |
root |
1.92 |
coroutine. Higher priority coroutines get run before lower priority |
537 |
|
|
coroutines. Priorities are small signed integers (currently -4 .. +3), |
538 |
root |
1.41 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
539 |
|
|
to get then): |
540 |
root |
1.31 |
|
541 |
|
|
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
542 |
|
|
3 > 1 > 0 > -1 > -3 > -4 |
543 |
|
|
|
544 |
|
|
# set priority to HIGH |
545 |
|
|
current->prio(PRIO_HIGH); |
546 |
|
|
|
547 |
|
|
The idle coroutine ($Coro::idle) always has a lower priority than any |
548 |
|
|
existing coroutine. |
549 |
|
|
|
550 |
root |
1.92 |
Changing the priority of the current coroutine will take effect immediately, |
551 |
|
|
but changing the priority of coroutines in the ready queue (but not |
552 |
root |
1.31 |
running) will only take effect after the next schedule (of that |
553 |
root |
1.92 |
coroutine). This is a bug that will be fixed in some future version. |
554 |
root |
1.31 |
|
555 |
root |
1.92 |
=item $newprio = $coroutine->nice ($change) |
556 |
root |
1.31 |
|
557 |
|
|
Similar to C<prio>, but subtract the given value from the priority (i.e. |
558 |
|
|
higher values mean lower priority, just as in unix). |
559 |
|
|
|
560 |
root |
1.92 |
=item $olddesc = $coroutine->desc ($newdesc) |
561 |
root |
1.41 |
|
562 |
|
|
Sets (or gets in case the argument is missing) the description for this |
563 |
root |
1.208 |
coroutine. This is just a free-form string you can associate with a |
564 |
|
|
coroutine. |
565 |
root |
1.150 |
|
566 |
root |
1.208 |
This method simply sets the C<< $coroutine->{desc} >> member to the given |
567 |
|
|
string. You can modify this member directly if you wish. |
568 |
root |
1.150 |
|
569 |
root |
1.41 |
=cut |
570 |
|
|
|
571 |
|
|
sub desc { |
572 |
|
|
my $old = $_[0]{desc}; |
573 |
|
|
$_[0]{desc} = $_[1] if @_ > 1; |
574 |
|
|
$old; |
575 |
root |
1.8 |
} |
576 |
root |
1.1 |
|
577 |
root |
1.233 |
sub transfer { |
578 |
|
|
require Carp; |
579 |
|
|
Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
580 |
|
|
} |
581 |
|
|
|
582 |
root |
1.8 |
=back |
583 |
root |
1.2 |
|
584 |
root |
1.234 |
=head1 GLOBAL FUNCTIONS |
585 |
root |
1.92 |
|
586 |
|
|
=over 4 |
587 |
|
|
|
588 |
root |
1.97 |
=item Coro::nready |
589 |
|
|
|
590 |
|
|
Returns the number of coroutines that are currently in the ready state, |
591 |
root |
1.181 |
i.e. that can be switched to by calling C<schedule> directory or |
592 |
|
|
indirectly. The value C<0> means that the only runnable coroutine is the |
593 |
|
|
currently running one, so C<cede> would have no effect, and C<schedule> |
594 |
|
|
would cause a deadlock unless there is an idle handler that wakes up some |
595 |
|
|
coroutines. |
596 |
root |
1.97 |
|
597 |
root |
1.103 |
=item my $guard = Coro::guard { ... } |
598 |
|
|
|
599 |
root |
1.243 |
This function still exists, but is deprecated. Please use the |
600 |
|
|
C<Guard::guard> function instead. |
601 |
root |
1.103 |
|
602 |
|
|
=cut |
603 |
|
|
|
604 |
root |
1.243 |
BEGIN { *guard = \&Guard::guard } |
605 |
root |
1.103 |
|
606 |
root |
1.92 |
=item unblock_sub { ... } |
607 |
|
|
|
608 |
|
|
This utility function takes a BLOCK or code reference and "unblocks" it, |
609 |
root |
1.181 |
returning a new coderef. Unblocking means that calling the new coderef |
610 |
|
|
will return immediately without blocking, returning nothing, while the |
611 |
|
|
original code ref will be called (with parameters) from within another |
612 |
|
|
coroutine. |
613 |
root |
1.92 |
|
614 |
root |
1.124 |
The reason this function exists is that many event libraries (such as the |
615 |
root |
1.92 |
venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
616 |
root |
1.238 |
of reentrancy). This means you must not block within event callbacks, |
617 |
root |
1.181 |
otherwise you might suffer from crashes or worse. The only event library |
618 |
|
|
currently known that is safe to use without C<unblock_sub> is L<EV>. |
619 |
root |
1.92 |
|
620 |
|
|
This function allows your callbacks to block by executing them in another |
621 |
|
|
coroutine where it is safe to block. One example where blocking is handy |
622 |
|
|
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
623 |
root |
1.181 |
disk, for example. |
624 |
root |
1.92 |
|
625 |
|
|
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
626 |
|
|
creating event callbacks that want to block. |
627 |
|
|
|
628 |
root |
1.181 |
If your handler does not plan to block (e.g. simply sends a message to |
629 |
|
|
another coroutine, or puts some other coroutine into the ready queue), |
630 |
|
|
there is no reason to use C<unblock_sub>. |
631 |
|
|
|
632 |
root |
1.183 |
Note that you also need to use C<unblock_sub> for any other callbacks that |
633 |
|
|
are indirectly executed by any C-based event loop. For example, when you |
634 |
|
|
use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
635 |
|
|
provides callbacks that are the result of some event callback, then you |
636 |
|
|
must not block either, or use C<unblock_sub>. |
637 |
|
|
|
638 |
root |
1.92 |
=cut |
639 |
|
|
|
640 |
|
|
our @unblock_queue; |
641 |
|
|
|
642 |
root |
1.105 |
# we create a special coro because we want to cede, |
643 |
|
|
# to reduce pressure on the coro pool (because most callbacks |
644 |
|
|
# return immediately and can be reused) and because we cannot cede |
645 |
|
|
# inside an event callback. |
646 |
root |
1.132 |
our $unblock_scheduler = new Coro sub { |
647 |
root |
1.92 |
while () { |
648 |
|
|
while (my $cb = pop @unblock_queue) { |
649 |
root |
1.227 |
&async_pool (@$cb); |
650 |
root |
1.105 |
|
651 |
root |
1.227 |
# for short-lived callbacks, this reduces pressure on the coro pool |
652 |
|
|
# as the chance is very high that the async_poll coro will be back |
653 |
|
|
# in the idle state when cede returns |
654 |
|
|
cede; |
655 |
root |
1.92 |
} |
656 |
root |
1.105 |
schedule; # sleep well |
657 |
root |
1.92 |
} |
658 |
|
|
}; |
659 |
root |
1.208 |
$unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
660 |
root |
1.92 |
|
661 |
|
|
sub unblock_sub(&) { |
662 |
|
|
my $cb = shift; |
663 |
|
|
|
664 |
|
|
sub { |
665 |
root |
1.105 |
unshift @unblock_queue, [$cb, @_]; |
666 |
root |
1.92 |
$unblock_scheduler->ready; |
667 |
|
|
} |
668 |
|
|
} |
669 |
|
|
|
670 |
root |
1.224 |
=item $cb = Coro::rouse_cb |
671 |
|
|
|
672 |
root |
1.238 |
Create and return a "rouse callback". That's a code reference that, |
673 |
|
|
when called, will remember a copy of its arguments and notify the owner |
674 |
|
|
coroutine of the callback. |
675 |
root |
1.224 |
|
676 |
|
|
See the next function. |
677 |
|
|
|
678 |
|
|
=item @args = Coro::rouse_wait [$cb] |
679 |
|
|
|
680 |
root |
1.238 |
Wait for the specified rouse callback (or the last one that was created in |
681 |
root |
1.224 |
this coroutine). |
682 |
|
|
|
683 |
root |
1.238 |
As soon as the callback is invoked (or when the callback was invoked |
684 |
|
|
before C<rouse_wait>), it will return the arguments originally passed to |
685 |
|
|
the rouse callback. |
686 |
root |
1.224 |
|
687 |
|
|
See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
688 |
|
|
|
689 |
root |
1.92 |
=back |
690 |
|
|
|
691 |
root |
1.8 |
=cut |
692 |
root |
1.2 |
|
693 |
root |
1.8 |
1; |
694 |
root |
1.14 |
|
695 |
root |
1.224 |
=head1 HOW TO WAIT FOR A CALLBACK |
696 |
|
|
|
697 |
|
|
It is very common for a coroutine to wait for some callback to be |
698 |
|
|
called. This occurs naturally when you use coroutines in an otherwise |
699 |
|
|
event-based program, or when you use event-based libraries. |
700 |
|
|
|
701 |
|
|
These typically register a callback for some event, and call that callback |
702 |
|
|
when the event occured. In a coroutine, however, you typically want to |
703 |
|
|
just wait for the event, simplyifying things. |
704 |
|
|
|
705 |
|
|
For example C<< AnyEvent->child >> registers a callback to be called when |
706 |
|
|
a specific child has exited: |
707 |
|
|
|
708 |
|
|
my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
709 |
|
|
|
710 |
|
|
But from withina coroutine, you often just want to write this: |
711 |
|
|
|
712 |
|
|
my $status = wait_for_child $pid; |
713 |
|
|
|
714 |
|
|
Coro offers two functions specifically designed to make this easy, |
715 |
|
|
C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
716 |
|
|
|
717 |
|
|
The first function, C<rouse_cb>, generates and returns a callback that, |
718 |
root |
1.240 |
when invoked, will save its arguments and notify the coroutine that |
719 |
root |
1.224 |
created the callback. |
720 |
|
|
|
721 |
|
|
The second function, C<rouse_wait>, waits for the callback to be called |
722 |
|
|
(by calling C<schedule> to go to sleep) and returns the arguments |
723 |
|
|
originally passed to the callback. |
724 |
|
|
|
725 |
|
|
Using these functions, it becomes easy to write the C<wait_for_child> |
726 |
|
|
function mentioned above: |
727 |
|
|
|
728 |
|
|
sub wait_for_child($) { |
729 |
|
|
my ($pid) = @_; |
730 |
|
|
|
731 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
732 |
|
|
|
733 |
|
|
my ($rpid, $rstatus) = Coro::rouse_wait; |
734 |
|
|
$rstatus |
735 |
|
|
} |
736 |
|
|
|
737 |
|
|
In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
738 |
|
|
you can roll your own, using C<schedule>: |
739 |
|
|
|
740 |
|
|
sub wait_for_child($) { |
741 |
|
|
my ($pid) = @_; |
742 |
|
|
|
743 |
|
|
# store the current coroutine in $current, |
744 |
|
|
# and provide result variables for the closure passed to ->child |
745 |
|
|
my $current = $Coro::current; |
746 |
|
|
my ($done, $rstatus); |
747 |
|
|
|
748 |
|
|
# pass a closure to ->child |
749 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
750 |
|
|
$rstatus = $_[1]; # remember rstatus |
751 |
|
|
$done = 1; # mark $rstatus as valud |
752 |
|
|
}); |
753 |
|
|
|
754 |
|
|
# wait until the closure has been called |
755 |
|
|
schedule while !$done; |
756 |
|
|
|
757 |
|
|
$rstatus |
758 |
|
|
} |
759 |
|
|
|
760 |
|
|
|
761 |
root |
1.17 |
=head1 BUGS/LIMITATIONS |
762 |
root |
1.14 |
|
763 |
root |
1.217 |
=over 4 |
764 |
|
|
|
765 |
root |
1.219 |
=item fork with pthread backend |
766 |
|
|
|
767 |
|
|
When Coro is compiled using the pthread backend (which isn't recommended |
768 |
|
|
but required on many BSDs as their libcs are completely broken), then |
769 |
|
|
coroutines will not survive a fork. There is no known workaround except to |
770 |
|
|
fix your libc and use a saner backend. |
771 |
|
|
|
772 |
root |
1.217 |
=item perl process emulation ("threads") |
773 |
|
|
|
774 |
root |
1.181 |
This module is not perl-pseudo-thread-safe. You should only ever use this |
775 |
root |
1.238 |
module from the first thread (this requirement might be removed in the |
776 |
root |
1.181 |
future to allow per-thread schedulers, but Coro::State does not yet allow |
777 |
root |
1.217 |
this). I recommend disabling thread support and using processes, as having |
778 |
|
|
the windows process emulation enabled under unix roughly halves perl |
779 |
|
|
performance, even when not used. |
780 |
|
|
|
781 |
|
|
=item coroutine switching not signal safe |
782 |
|
|
|
783 |
|
|
You must not switch to another coroutine from within a signal handler |
784 |
|
|
(only relevant with %SIG - most event libraries provide safe signals). |
785 |
|
|
|
786 |
root |
1.221 |
That means you I<MUST NOT> call any function that might "block" the |
787 |
root |
1.217 |
current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
788 |
|
|
anything that calls those. Everything else, including calling C<ready>, |
789 |
|
|
works. |
790 |
|
|
|
791 |
|
|
=back |
792 |
|
|
|
793 |
root |
1.9 |
|
794 |
|
|
=head1 SEE ALSO |
795 |
|
|
|
796 |
root |
1.181 |
Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
797 |
root |
1.152 |
|
798 |
|
|
Debugging: L<Coro::Debug>. |
799 |
|
|
|
800 |
|
|
Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
801 |
root |
1.67 |
|
802 |
root |
1.238 |
Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
803 |
root |
1.235 |
L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
804 |
root |
1.67 |
|
805 |
root |
1.238 |
I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
806 |
root |
1.181 |
|
807 |
root |
1.238 |
Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
808 |
root |
1.235 |
a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
809 |
|
|
L<Coro::Select>. |
810 |
root |
1.152 |
|
811 |
root |
1.181 |
XS API: L<Coro::MakeMaker>. |
812 |
root |
1.67 |
|
813 |
root |
1.238 |
Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
814 |
root |
1.1 |
|
815 |
|
|
=head1 AUTHOR |
816 |
|
|
|
817 |
root |
1.66 |
Marc Lehmann <schmorp@schmorp.de> |
818 |
root |
1.64 |
http://home.schmorp.de/ |
819 |
root |
1.1 |
|
820 |
|
|
=cut |
821 |
|
|
|