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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 coro |
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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 in |
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the form of cooperative threads (also called coros, or simply "coro" |
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in the documentation). They are similar to kernel threads but don't (in |
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general) run in parallel at the same time even on SMP machines. The |
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specific flavor of thread offered by this module also guarantees you that |
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it will not switch between threads unless necessary, at easily-identified |
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points in your program, so locking and parallel access are rarely an |
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issue, making thread programming much safer and easier than using other |
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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 (see section of same name for more |
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details) ported to unix, and as such act as processes), Coro provides |
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a full shared address space, which makes communication between threads |
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very easy. And Coro's threads are fast, too: disabling the Windows |
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process emulation code in your perl and using Coro can easily result in |
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a two to four times speed increase for your programs. A parallel matrix |
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multiplication benchmark runs over 300 times faster on a single core than |
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perl's pseudo-threads on a quad core using all four cores. |
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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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some package variables + 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 common::sense; |
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use Carp (); |
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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 coro |
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our $current; # current coro |
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|
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our $VERSION = 5.25; |
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|
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our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub rouse_cb rouse_wait); |
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our %EXPORT_TAGS = ( |
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prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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); |
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our @EXPORT_OK = (@{$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 $Coro::main |
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|
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This variable stores the Coro object that represents the main |
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program. While you cna C<ready> it and do most other things you can do to |
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coro, it is mainly useful to compare again C<$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 $Coro::current |
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|
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The Coro object representing the current coro (the last |
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coro that the Coro scheduler switched to). The initial value is |
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C<$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 Coro 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 $Coro::idle |
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|
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This variable is mainly useful to integrate Coro into event loops. It is |
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usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is |
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pretty low-level functionality. |
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This variable stores a Coro object that is put into the ready queue when |
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there are no other ready threads (without invoking any ready hooks). |
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|
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The default implementation dies with "FATAL: deadlock detected.", followed |
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by a thread listing, because the program has no other way to continue. |
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This hook is overwritten by modules such as C<Coro::EV> and |
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C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
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coro so the scheduler can run it. |
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|
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See L<Coro::EV> or L<Coro::AnyEvent> for examples of using this technique. |
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|
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=cut |
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# ||= because other modules could have provided their own by now |
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$idle ||= new Coro sub { |
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require Coro::Debug; |
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die "FATAL: deadlock detected.\n" |
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. Coro::Debug::ps_listing (); |
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}; |
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|
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# this coro is necessary because a coro |
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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::State::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 CORO CREATION |
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|
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=over 4 |
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=item async { ... } [@args...] |
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|
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Create a new coro and return its Coro object (usually |
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unused). The coro 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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coro. When it returns argument returns the coro 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 coro |
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environment in which coro are executed. |
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|
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Calling C<exit> in a coro will do the same as calling exit outside |
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the coro. Likewise, when the coro 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 coro that just prints its arguments. |
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|
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async { |
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print "@_\n"; |
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} 1,2,3,4; |
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=item async_pool { ... } [@args...] |
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Similar to C<async>, but uses a coro 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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coro 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 coro, so if you need a lot of generic |
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coros in quick successsion, use C<async_pool>, not C<async>. |
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|
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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 coro 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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|
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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 coro will |
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be re-used "as-is": most notably if you change other per-coro 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 coros (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 coros 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 $@; |
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} |
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} |
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|
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=back |
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=head1 STATIC METHODS |
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|
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Static methods are actually functions that implicitly operate on the |
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current coro. |
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|
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=over 4 |
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=item schedule |
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1.6 |
|
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Calls the scheduler. The scheduler will find the next coro that is |
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to be run from the ready queue and switches to it. The next coro |
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to be run is simply the one with the highest priority that is longest |
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in its ready queue. If there is no coro ready, it will call the |
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C<$Coro::idle> hook. |
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|
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Please note that the current coro 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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coro and wait for events: first you remember the current coro 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 coro 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 coros. This function puts the current coro 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 coros of the same or higher |
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priority. Once your coro gets its turn again it will automatically be |
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resumed. |
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This function is often called C<yield> in other languages. |
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1.7 |
|
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=item Coro::cede_notself |
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|
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Works like cede, but is not exported by default and will cede to I<any> |
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coro, regardless of priority. This is useful sometimes to ensure |
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1.181 |
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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1.248 |
Terminates the current coro 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 |
304 |
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|
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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 coro is re-entered by the scheduler, while the leave block is |
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executed whenever the current coro 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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|
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I<Neither invoking the scheduler, nor exceptions, are allowed within those |
313 |
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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. |
315 |
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|
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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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|
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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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coro. |
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|
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1.254 |
They slow down thread switching considerably for coros that use them |
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(about 40% for a BLOCK with a single assignment, so thread switching is |
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still reasonably fast if the handlers are fast). |
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|
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These functions are best understood by an example: The following function |
328 |
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will change the current timezone to "Antarctica/South_Pole", which |
329 |
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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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1.252 |
value, respectively, the timezone is only changed for the coro that |
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1.247 |
installed those handlers. |
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|
334 |
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use POSIX qw(tzset); |
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336 |
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async { |
337 |
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my $old_tz; # store outside TZ value here |
338 |
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339 |
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Coro::on_enter { |
340 |
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$old_tz = $ENV{TZ}; # remember the old value |
341 |
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342 |
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$ENV{TZ} = "Antarctica/South_Pole"; |
343 |
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tzset; # enable new value |
344 |
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}; |
345 |
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346 |
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Coro::on_leave { |
347 |
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$ENV{TZ} = $old_tz; |
348 |
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tzset; # restore old value |
349 |
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}; |
350 |
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|
351 |
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# at this place, the timezone is Antarctica/South_Pole, |
352 |
root |
1.248 |
# without disturbing the TZ of any other coro. |
353 |
root |
1.247 |
}; |
354 |
|
|
|
355 |
|
|
This can be used to localise about any resource (locale, uid, current |
356 |
|
|
working directory etc.) to a block, despite the existance of other |
357 |
root |
1.248 |
coros. |
358 |
root |
1.247 |
|
359 |
root |
1.255 |
Another interesting example implements time-sliced multitasking using |
360 |
|
|
interval timers (this could obviously be optimised, but does the job): |
361 |
|
|
|
362 |
|
|
# "timeslice" the given block |
363 |
|
|
sub timeslice(&) { |
364 |
|
|
use Time::HiRes (); |
365 |
|
|
|
366 |
|
|
Coro::on_enter { |
367 |
|
|
# on entering the thread, we set an VTALRM handler to cede |
368 |
|
|
$SIG{VTALRM} = sub { cede }; |
369 |
|
|
# and then start the interval timer |
370 |
|
|
Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; |
371 |
|
|
}; |
372 |
|
|
Coro::on_leave { |
373 |
|
|
# on leaving the thread, we stop the interval timer again |
374 |
|
|
Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; |
375 |
|
|
}; |
376 |
|
|
|
377 |
|
|
&{+shift}; |
378 |
|
|
} |
379 |
|
|
|
380 |
|
|
# use like this: |
381 |
|
|
timeslice { |
382 |
|
|
# The following is an endless loop that would normally |
383 |
root |
1.256 |
# monopolise the process. Since it runs in a timesliced |
384 |
root |
1.255 |
# environment, it will regularly cede to other threads. |
385 |
|
|
while () { } |
386 |
|
|
}; |
387 |
|
|
|
388 |
|
|
|
389 |
root |
1.141 |
=item killall |
390 |
|
|
|
391 |
root |
1.248 |
Kills/terminates/cancels all coros except the currently running one. |
392 |
root |
1.247 |
|
393 |
|
|
Note that while this will try to free some of the main interpreter |
394 |
root |
1.248 |
resources if the calling coro isn't the main coro, but one |
395 |
|
|
cannot free all of them, so if a coro that is not the main coro |
396 |
root |
1.247 |
calls this function, there will be some one-time resource leak. |
397 |
root |
1.181 |
|
398 |
root |
1.1 |
=cut |
399 |
|
|
|
400 |
root |
1.141 |
sub killall { |
401 |
|
|
for (Coro::State::list) { |
402 |
|
|
$_->cancel |
403 |
|
|
if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
404 |
|
|
} |
405 |
|
|
} |
406 |
|
|
|
407 |
root |
1.8 |
=back |
408 |
|
|
|
409 |
root |
1.248 |
=head1 CORO OBJECT METHODS |
410 |
root |
1.8 |
|
411 |
root |
1.248 |
These are the methods you can call on coro objects (or to create |
412 |
root |
1.181 |
them). |
413 |
root |
1.6 |
|
414 |
root |
1.8 |
=over 4 |
415 |
|
|
|
416 |
root |
1.13 |
=item new Coro \&sub [, @args...] |
417 |
root |
1.8 |
|
418 |
root |
1.248 |
Create a new coro and return it. When the sub returns, the coro |
419 |
root |
1.40 |
automatically terminates as if C<terminate> with the returned values were |
420 |
root |
1.248 |
called. To make the coro run you must first put it into the ready |
421 |
root |
1.181 |
queue by calling the ready method. |
422 |
root |
1.13 |
|
423 |
root |
1.145 |
See C<async> and C<Coro::State::new> for additional info about the |
424 |
root |
1.248 |
coro environment. |
425 |
root |
1.89 |
|
426 |
root |
1.6 |
=cut |
427 |
|
|
|
428 |
root |
1.241 |
sub _coro_run { |
429 |
root |
1.13 |
terminate &{+shift}; |
430 |
|
|
} |
431 |
|
|
|
432 |
root |
1.248 |
=item $success = $coro->ready |
433 |
root |
1.1 |
|
434 |
root |
1.248 |
Put the given coro into the end of its ready queue (there is one |
435 |
|
|
queue for each priority) and return true. If the coro is already in |
436 |
root |
1.181 |
the ready queue, do nothing and return false. |
437 |
|
|
|
438 |
root |
1.248 |
This ensures that the scheduler will resume this coro automatically |
439 |
|
|
once all the coro of higher priority and all coro of the same |
440 |
root |
1.181 |
priority that were put into the ready queue earlier have been resumed. |
441 |
root |
1.1 |
|
442 |
root |
1.250 |
=item $coro->suspend |
443 |
|
|
|
444 |
|
|
Suspends the specified coro. A suspended coro works just like any other |
445 |
|
|
coro, except that the scheduler will not select a suspended coro for |
446 |
|
|
execution. |
447 |
|
|
|
448 |
|
|
Suspending a coro can be useful when you want to keep the coro from |
449 |
|
|
running, but you don't want to destroy it, or when you want to temporarily |
450 |
|
|
freeze a coro (e.g. for debugging) to resume it later. |
451 |
|
|
|
452 |
|
|
A scenario for the former would be to suspend all (other) coros after a |
453 |
|
|
fork and keep them alive, so their destructors aren't called, but new |
454 |
|
|
coros can be created. |
455 |
|
|
|
456 |
|
|
=item $coro->resume |
457 |
|
|
|
458 |
|
|
If the specified coro was suspended, it will be resumed. Note that when |
459 |
|
|
the coro was in the ready queue when it was suspended, it might have been |
460 |
|
|
unreadied by the scheduler, so an activation might have been lost. |
461 |
|
|
|
462 |
|
|
To avoid this, it is best to put a suspended coro into the ready queue |
463 |
|
|
unconditionally, as every synchronisation mechanism must protect itself |
464 |
|
|
against spurious wakeups, and the one in the Coro family certainly do |
465 |
|
|
that. |
466 |
|
|
|
467 |
root |
1.248 |
=item $is_ready = $coro->is_ready |
468 |
root |
1.90 |
|
469 |
root |
1.248 |
Returns true iff the Coro object is in the ready queue. Unless the Coro |
470 |
|
|
object gets destroyed, it will eventually be scheduled by the scheduler. |
471 |
root |
1.28 |
|
472 |
root |
1.248 |
=item $is_running = $coro->is_running |
473 |
root |
1.28 |
|
474 |
root |
1.248 |
Returns true iff the Coro object is currently running. Only one Coro object |
475 |
|
|
can ever be in the running state (but it currently is possible to have |
476 |
|
|
multiple running Coro::States). |
477 |
|
|
|
478 |
|
|
=item $is_suspended = $coro->is_suspended |
479 |
|
|
|
480 |
|
|
Returns true iff this Coro object has been suspended. Suspended Coros will |
481 |
|
|
not ever be scheduled. |
482 |
|
|
|
483 |
|
|
=item $coro->cancel (arg...) |
484 |
|
|
|
485 |
|
|
Terminates the given Coro and makes it return the given arguments as |
486 |
|
|
status (default: the empty list). Never returns if the Coro is the |
487 |
|
|
current Coro. |
488 |
root |
1.28 |
|
489 |
|
|
=cut |
490 |
|
|
|
491 |
|
|
sub cancel { |
492 |
pcg |
1.59 |
my $self = shift; |
493 |
root |
1.103 |
|
494 |
|
|
if ($current == $self) { |
495 |
root |
1.226 |
terminate @_; |
496 |
root |
1.103 |
} else { |
497 |
root |
1.226 |
$self->{_status} = [@_]; |
498 |
root |
1.248 |
Coro::State::cancel $self; |
499 |
root |
1.103 |
} |
500 |
root |
1.40 |
} |
501 |
|
|
|
502 |
root |
1.248 |
=item $coro->schedule_to |
503 |
root |
1.229 |
|
504 |
root |
1.248 |
Puts the current coro to sleep (like C<Coro::schedule>), but instead |
505 |
root |
1.229 |
of continuing with the next coro from the ready queue, always switch to |
506 |
root |
1.248 |
the given coro object (regardless of priority etc.). The readyness |
507 |
|
|
state of that coro isn't changed. |
508 |
root |
1.229 |
|
509 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
510 |
|
|
uses for this one. |
511 |
|
|
|
512 |
root |
1.248 |
=item $coro->cede_to |
513 |
root |
1.229 |
|
514 |
root |
1.248 |
Like C<schedule_to>, but puts the current coro into the ready |
515 |
root |
1.229 |
queue. This has the effect of temporarily switching to the given |
516 |
root |
1.248 |
coro, and continuing some time later. |
517 |
root |
1.229 |
|
518 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
519 |
|
|
uses for this one. |
520 |
|
|
|
521 |
root |
1.248 |
=item $coro->throw ([$scalar]) |
522 |
root |
1.208 |
|
523 |
|
|
If C<$throw> is specified and defined, it will be thrown as an exception |
524 |
root |
1.248 |
inside the coro at the next convenient point in time. Otherwise |
525 |
root |
1.222 |
clears the exception object. |
526 |
|
|
|
527 |
|
|
Coro will check for the exception each time a schedule-like-function |
528 |
|
|
returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
529 |
root |
1.223 |
>>, C<< Coro::Handle->readable >> and so on. Most of these functions |
530 |
|
|
detect this case and return early in case an exception is pending. |
531 |
root |
1.208 |
|
532 |
|
|
The exception object will be thrown "as is" with the specified scalar in |
533 |
|
|
C<$@>, i.e. if it is a string, no line number or newline will be appended |
534 |
|
|
(unlike with C<die>). |
535 |
|
|
|
536 |
root |
1.248 |
This can be used as a softer means than C<cancel> to ask a coro to |
537 |
root |
1.208 |
end itself, although there is no guarantee that the exception will lead to |
538 |
|
|
termination, and if the exception isn't caught it might well end the whole |
539 |
|
|
program. |
540 |
|
|
|
541 |
|
|
You might also think of C<throw> as being the moral equivalent of |
542 |
root |
1.248 |
C<kill>ing a coro with a signal (in this case, a scalar). |
543 |
root |
1.208 |
|
544 |
root |
1.248 |
=item $coro->join |
545 |
root |
1.40 |
|
546 |
root |
1.248 |
Wait until the coro terminates and return any values given to the |
547 |
root |
1.143 |
C<terminate> or C<cancel> functions. C<join> can be called concurrently |
548 |
root |
1.248 |
from multiple coro, and all will be resumed and given the status |
549 |
|
|
return once the C<$coro> terminates. |
550 |
root |
1.40 |
|
551 |
|
|
=cut |
552 |
|
|
|
553 |
|
|
sub join { |
554 |
|
|
my $self = shift; |
555 |
root |
1.103 |
|
556 |
root |
1.142 |
unless ($self->{_status}) { |
557 |
root |
1.103 |
my $current = $current; |
558 |
|
|
|
559 |
root |
1.142 |
push @{$self->{_on_destroy}}, sub { |
560 |
root |
1.103 |
$current->ready; |
561 |
|
|
undef $current; |
562 |
|
|
}; |
563 |
|
|
|
564 |
|
|
&schedule while $current; |
565 |
root |
1.40 |
} |
566 |
root |
1.103 |
|
567 |
root |
1.142 |
wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
568 |
root |
1.31 |
} |
569 |
|
|
|
570 |
root |
1.248 |
=item $coro->on_destroy (\&cb) |
571 |
root |
1.101 |
|
572 |
root |
1.248 |
Registers a callback that is called when this coro gets destroyed, |
573 |
root |
1.101 |
but before it is joined. The callback gets passed the terminate arguments, |
574 |
root |
1.181 |
if any, and I<must not> die, under any circumstances. |
575 |
root |
1.101 |
|
576 |
|
|
=cut |
577 |
|
|
|
578 |
|
|
sub on_destroy { |
579 |
|
|
my ($self, $cb) = @_; |
580 |
|
|
|
581 |
root |
1.142 |
push @{ $self->{_on_destroy} }, $cb; |
582 |
root |
1.101 |
} |
583 |
|
|
|
584 |
root |
1.248 |
=item $oldprio = $coro->prio ($newprio) |
585 |
root |
1.31 |
|
586 |
root |
1.41 |
Sets (or gets, if the argument is missing) the priority of the |
587 |
root |
1.248 |
coro. Higher priority coro get run before lower priority |
588 |
|
|
coro. Priorities are small signed integers (currently -4 .. +3), |
589 |
root |
1.41 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
590 |
|
|
to get then): |
591 |
root |
1.31 |
|
592 |
|
|
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
593 |
|
|
3 > 1 > 0 > -1 > -3 > -4 |
594 |
|
|
|
595 |
|
|
# set priority to HIGH |
596 |
root |
1.248 |
current->prio (PRIO_HIGH); |
597 |
root |
1.31 |
|
598 |
root |
1.248 |
The idle coro ($Coro::idle) always has a lower priority than any |
599 |
|
|
existing coro. |
600 |
root |
1.31 |
|
601 |
root |
1.248 |
Changing the priority of the current coro will take effect immediately, |
602 |
|
|
but changing the priority of coro in the ready queue (but not |
603 |
root |
1.31 |
running) will only take effect after the next schedule (of that |
604 |
root |
1.248 |
coro). This is a bug that will be fixed in some future version. |
605 |
root |
1.31 |
|
606 |
root |
1.248 |
=item $newprio = $coro->nice ($change) |
607 |
root |
1.31 |
|
608 |
|
|
Similar to C<prio>, but subtract the given value from the priority (i.e. |
609 |
|
|
higher values mean lower priority, just as in unix). |
610 |
|
|
|
611 |
root |
1.248 |
=item $olddesc = $coro->desc ($newdesc) |
612 |
root |
1.41 |
|
613 |
|
|
Sets (or gets in case the argument is missing) the description for this |
614 |
root |
1.248 |
coro. This is just a free-form string you can associate with a |
615 |
|
|
coro. |
616 |
root |
1.150 |
|
617 |
root |
1.248 |
This method simply sets the C<< $coro->{desc} >> member to the given |
618 |
root |
1.280 |
string. You can modify this member directly if you wish, and in fact, this |
619 |
|
|
is often preferred to indicate major processing states that cna then be |
620 |
|
|
seen for example in a L<Coro::Debug> session: |
621 |
|
|
|
622 |
|
|
sub my_long_function { |
623 |
|
|
local $Coro::current->{desc} = "now in my_long_function"; |
624 |
|
|
... |
625 |
|
|
$Coro::current->{desc} = "my_long_function: phase 1"; |
626 |
|
|
... |
627 |
|
|
$Coro::current->{desc} = "my_long_function: phase 2"; |
628 |
|
|
... |
629 |
|
|
} |
630 |
root |
1.150 |
|
631 |
root |
1.41 |
=cut |
632 |
|
|
|
633 |
|
|
sub desc { |
634 |
|
|
my $old = $_[0]{desc}; |
635 |
|
|
$_[0]{desc} = $_[1] if @_ > 1; |
636 |
|
|
$old; |
637 |
root |
1.8 |
} |
638 |
root |
1.1 |
|
639 |
root |
1.233 |
sub transfer { |
640 |
|
|
require Carp; |
641 |
|
|
Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
642 |
|
|
} |
643 |
|
|
|
644 |
root |
1.8 |
=back |
645 |
root |
1.2 |
|
646 |
root |
1.234 |
=head1 GLOBAL FUNCTIONS |
647 |
root |
1.92 |
|
648 |
|
|
=over 4 |
649 |
|
|
|
650 |
root |
1.97 |
=item Coro::nready |
651 |
|
|
|
652 |
root |
1.248 |
Returns the number of coro that are currently in the ready state, |
653 |
root |
1.181 |
i.e. that can be switched to by calling C<schedule> directory or |
654 |
root |
1.248 |
indirectly. The value C<0> means that the only runnable coro is the |
655 |
root |
1.181 |
currently running one, so C<cede> would have no effect, and C<schedule> |
656 |
|
|
would cause a deadlock unless there is an idle handler that wakes up some |
657 |
root |
1.248 |
coro. |
658 |
root |
1.97 |
|
659 |
root |
1.103 |
=item my $guard = Coro::guard { ... } |
660 |
|
|
|
661 |
root |
1.243 |
This function still exists, but is deprecated. Please use the |
662 |
|
|
C<Guard::guard> function instead. |
663 |
root |
1.103 |
|
664 |
|
|
=cut |
665 |
|
|
|
666 |
root |
1.243 |
BEGIN { *guard = \&Guard::guard } |
667 |
root |
1.103 |
|
668 |
root |
1.92 |
=item unblock_sub { ... } |
669 |
|
|
|
670 |
|
|
This utility function takes a BLOCK or code reference and "unblocks" it, |
671 |
root |
1.181 |
returning a new coderef. Unblocking means that calling the new coderef |
672 |
|
|
will return immediately without blocking, returning nothing, while the |
673 |
|
|
original code ref will be called (with parameters) from within another |
674 |
root |
1.248 |
coro. |
675 |
root |
1.92 |
|
676 |
root |
1.282 |
The reason this function exists is that many event libraries (such as |
677 |
|
|
the venerable L<Event|Event> module) are not thread-safe (a weaker form |
678 |
root |
1.238 |
of reentrancy). This means you must not block within event callbacks, |
679 |
root |
1.181 |
otherwise you might suffer from crashes or worse. The only event library |
680 |
root |
1.282 |
currently known that is safe to use without C<unblock_sub> is L<EV> (but |
681 |
|
|
you might still run into deadlocks if all event loops are blocked). |
682 |
root |
1.92 |
|
683 |
root |
1.274 |
Coro will try to catch you when you block in the event loop |
684 |
|
|
("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and |
685 |
|
|
only works when you do not run your own event loop. |
686 |
|
|
|
687 |
root |
1.92 |
This function allows your callbacks to block by executing them in another |
688 |
root |
1.248 |
coro where it is safe to block. One example where blocking is handy |
689 |
root |
1.92 |
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
690 |
root |
1.181 |
disk, for example. |
691 |
root |
1.92 |
|
692 |
|
|
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
693 |
|
|
creating event callbacks that want to block. |
694 |
|
|
|
695 |
root |
1.181 |
If your handler does not plan to block (e.g. simply sends a message to |
696 |
root |
1.248 |
another coro, or puts some other coro into the ready queue), there is |
697 |
|
|
no reason to use C<unblock_sub>. |
698 |
root |
1.181 |
|
699 |
root |
1.183 |
Note that you also need to use C<unblock_sub> for any other callbacks that |
700 |
|
|
are indirectly executed by any C-based event loop. For example, when you |
701 |
|
|
use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
702 |
|
|
provides callbacks that are the result of some event callback, then you |
703 |
|
|
must not block either, or use C<unblock_sub>. |
704 |
|
|
|
705 |
root |
1.92 |
=cut |
706 |
|
|
|
707 |
|
|
our @unblock_queue; |
708 |
|
|
|
709 |
root |
1.105 |
# we create a special coro because we want to cede, |
710 |
|
|
# to reduce pressure on the coro pool (because most callbacks |
711 |
|
|
# return immediately and can be reused) and because we cannot cede |
712 |
|
|
# inside an event callback. |
713 |
root |
1.132 |
our $unblock_scheduler = new Coro sub { |
714 |
root |
1.92 |
while () { |
715 |
|
|
while (my $cb = pop @unblock_queue) { |
716 |
root |
1.227 |
&async_pool (@$cb); |
717 |
root |
1.105 |
|
718 |
root |
1.227 |
# for short-lived callbacks, this reduces pressure on the coro pool |
719 |
|
|
# as the chance is very high that the async_poll coro will be back |
720 |
|
|
# in the idle state when cede returns |
721 |
|
|
cede; |
722 |
root |
1.92 |
} |
723 |
root |
1.105 |
schedule; # sleep well |
724 |
root |
1.92 |
} |
725 |
|
|
}; |
726 |
root |
1.208 |
$unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
727 |
root |
1.92 |
|
728 |
|
|
sub unblock_sub(&) { |
729 |
|
|
my $cb = shift; |
730 |
|
|
|
731 |
|
|
sub { |
732 |
root |
1.105 |
unshift @unblock_queue, [$cb, @_]; |
733 |
root |
1.92 |
$unblock_scheduler->ready; |
734 |
|
|
} |
735 |
|
|
} |
736 |
|
|
|
737 |
root |
1.271 |
=item $cb = rouse_cb |
738 |
root |
1.224 |
|
739 |
root |
1.238 |
Create and return a "rouse callback". That's a code reference that, |
740 |
|
|
when called, will remember a copy of its arguments and notify the owner |
741 |
root |
1.248 |
coro of the callback. |
742 |
root |
1.224 |
|
743 |
|
|
See the next function. |
744 |
|
|
|
745 |
root |
1.271 |
=item @args = rouse_wait [$cb] |
746 |
root |
1.224 |
|
747 |
root |
1.238 |
Wait for the specified rouse callback (or the last one that was created in |
748 |
root |
1.248 |
this coro). |
749 |
root |
1.224 |
|
750 |
root |
1.238 |
As soon as the callback is invoked (or when the callback was invoked |
751 |
|
|
before C<rouse_wait>), it will return the arguments originally passed to |
752 |
root |
1.258 |
the rouse callback. In scalar context, that means you get the I<last> |
753 |
|
|
argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)> |
754 |
|
|
statement at the end. |
755 |
root |
1.224 |
|
756 |
|
|
See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
757 |
|
|
|
758 |
root |
1.92 |
=back |
759 |
|
|
|
760 |
root |
1.8 |
=cut |
761 |
root |
1.2 |
|
762 |
root |
1.8 |
1; |
763 |
root |
1.14 |
|
764 |
root |
1.224 |
=head1 HOW TO WAIT FOR A CALLBACK |
765 |
|
|
|
766 |
root |
1.248 |
It is very common for a coro to wait for some callback to be |
767 |
|
|
called. This occurs naturally when you use coro in an otherwise |
768 |
root |
1.224 |
event-based program, or when you use event-based libraries. |
769 |
|
|
|
770 |
|
|
These typically register a callback for some event, and call that callback |
771 |
root |
1.248 |
when the event occured. In a coro, however, you typically want to |
772 |
root |
1.224 |
just wait for the event, simplyifying things. |
773 |
|
|
|
774 |
|
|
For example C<< AnyEvent->child >> registers a callback to be called when |
775 |
|
|
a specific child has exited: |
776 |
|
|
|
777 |
|
|
my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
778 |
|
|
|
779 |
root |
1.248 |
But from within a coro, you often just want to write this: |
780 |
root |
1.224 |
|
781 |
|
|
my $status = wait_for_child $pid; |
782 |
|
|
|
783 |
|
|
Coro offers two functions specifically designed to make this easy, |
784 |
|
|
C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
785 |
|
|
|
786 |
|
|
The first function, C<rouse_cb>, generates and returns a callback that, |
787 |
root |
1.248 |
when invoked, will save its arguments and notify the coro that |
788 |
root |
1.224 |
created the callback. |
789 |
|
|
|
790 |
|
|
The second function, C<rouse_wait>, waits for the callback to be called |
791 |
|
|
(by calling C<schedule> to go to sleep) and returns the arguments |
792 |
|
|
originally passed to the callback. |
793 |
|
|
|
794 |
|
|
Using these functions, it becomes easy to write the C<wait_for_child> |
795 |
|
|
function mentioned above: |
796 |
|
|
|
797 |
|
|
sub wait_for_child($) { |
798 |
|
|
my ($pid) = @_; |
799 |
|
|
|
800 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
801 |
|
|
|
802 |
|
|
my ($rpid, $rstatus) = Coro::rouse_wait; |
803 |
|
|
$rstatus |
804 |
|
|
} |
805 |
|
|
|
806 |
|
|
In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
807 |
|
|
you can roll your own, using C<schedule>: |
808 |
|
|
|
809 |
|
|
sub wait_for_child($) { |
810 |
|
|
my ($pid) = @_; |
811 |
|
|
|
812 |
root |
1.248 |
# store the current coro in $current, |
813 |
root |
1.224 |
# and provide result variables for the closure passed to ->child |
814 |
|
|
my $current = $Coro::current; |
815 |
|
|
my ($done, $rstatus); |
816 |
|
|
|
817 |
|
|
# pass a closure to ->child |
818 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
819 |
|
|
$rstatus = $_[1]; # remember rstatus |
820 |
|
|
$done = 1; # mark $rstatus as valud |
821 |
|
|
}); |
822 |
|
|
|
823 |
|
|
# wait until the closure has been called |
824 |
|
|
schedule while !$done; |
825 |
|
|
|
826 |
|
|
$rstatus |
827 |
|
|
} |
828 |
|
|
|
829 |
|
|
|
830 |
root |
1.17 |
=head1 BUGS/LIMITATIONS |
831 |
root |
1.14 |
|
832 |
root |
1.217 |
=over 4 |
833 |
|
|
|
834 |
root |
1.219 |
=item fork with pthread backend |
835 |
|
|
|
836 |
|
|
When Coro is compiled using the pthread backend (which isn't recommended |
837 |
|
|
but required on many BSDs as their libcs are completely broken), then |
838 |
root |
1.248 |
coro will not survive a fork. There is no known workaround except to |
839 |
root |
1.219 |
fix your libc and use a saner backend. |
840 |
|
|
|
841 |
root |
1.217 |
=item perl process emulation ("threads") |
842 |
|
|
|
843 |
root |
1.181 |
This module is not perl-pseudo-thread-safe. You should only ever use this |
844 |
root |
1.238 |
module from the first thread (this requirement might be removed in the |
845 |
root |
1.181 |
future to allow per-thread schedulers, but Coro::State does not yet allow |
846 |
root |
1.217 |
this). I recommend disabling thread support and using processes, as having |
847 |
|
|
the windows process emulation enabled under unix roughly halves perl |
848 |
|
|
performance, even when not used. |
849 |
|
|
|
850 |
root |
1.248 |
=item coro switching is not signal safe |
851 |
root |
1.217 |
|
852 |
root |
1.272 |
You must not switch to another coro from within a signal handler (only |
853 |
|
|
relevant with %SIG - most event libraries provide safe signals), I<unless> |
854 |
|
|
you are sure you are not interrupting a Coro function. |
855 |
root |
1.217 |
|
856 |
root |
1.221 |
That means you I<MUST NOT> call any function that might "block" the |
857 |
root |
1.248 |
current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
858 |
root |
1.217 |
anything that calls those. Everything else, including calling C<ready>, |
859 |
|
|
works. |
860 |
|
|
|
861 |
|
|
=back |
862 |
|
|
|
863 |
root |
1.9 |
|
864 |
root |
1.266 |
=head1 WINDOWS PROCESS EMULATION |
865 |
|
|
|
866 |
|
|
A great many people seem to be confused about ithreads (for example, Chip |
867 |
root |
1.267 |
Salzenberg called me unintelligent, incapable, stupid and gullible, |
868 |
root |
1.266 |
while in the same mail making rather confused statements about perl |
869 |
|
|
ithreads (for example, that memory or files would be shared), showing his |
870 |
|
|
lack of understanding of this area - if it is hard to understand for Chip, |
871 |
|
|
it is probably not obvious to everybody). |
872 |
|
|
|
873 |
|
|
What follows is an ultra-condensed version of my talk about threads in |
874 |
root |
1.281 |
scripting languages given on the perl workshop 2009: |
875 |
root |
1.266 |
|
876 |
|
|
The so-called "ithreads" were originally implemented for two reasons: |
877 |
|
|
first, to (badly) emulate unix processes on native win32 perls, and |
878 |
|
|
secondly, to replace the older, real thread model ("5.005-threads"). |
879 |
|
|
|
880 |
|
|
It does that by using threads instead of OS processes. The difference |
881 |
|
|
between processes and threads is that threads share memory (and other |
882 |
|
|
state, such as files) between threads within a single process, while |
883 |
|
|
processes do not share anything (at least not semantically). That |
884 |
|
|
means that modifications done by one thread are seen by others, while |
885 |
|
|
modifications by one process are not seen by other processes. |
886 |
|
|
|
887 |
|
|
The "ithreads" work exactly like that: when creating a new ithreads |
888 |
|
|
process, all state is copied (memory is copied physically, files and code |
889 |
|
|
is copied logically). Afterwards, it isolates all modifications. On UNIX, |
890 |
|
|
the same behaviour can be achieved by using operating system processes, |
891 |
|
|
except that UNIX typically uses hardware built into the system to do this |
892 |
|
|
efficiently, while the windows process emulation emulates this hardware in |
893 |
|
|
software (rather efficiently, but of course it is still much slower than |
894 |
|
|
dedicated hardware). |
895 |
|
|
|
896 |
|
|
As mentioned before, loading code, modifying code, modifying data |
897 |
|
|
structures and so on is only visible in the ithreads process doing the |
898 |
|
|
modification, not in other ithread processes within the same OS process. |
899 |
|
|
|
900 |
|
|
This is why "ithreads" do not implement threads for perl at all, only |
901 |
|
|
processes. What makes it so bad is that on non-windows platforms, you can |
902 |
|
|
actually take advantage of custom hardware for this purpose (as evidenced |
903 |
|
|
by the forks module, which gives you the (i-) threads API, just much |
904 |
|
|
faster). |
905 |
|
|
|
906 |
|
|
Sharing data is in the i-threads model is done by transfering data |
907 |
|
|
structures between threads using copying semantics, which is very slow - |
908 |
|
|
shared data simply does not exist. Benchmarks using i-threads which are |
909 |
|
|
communication-intensive show extremely bad behaviour with i-threads (in |
910 |
|
|
fact, so bad that Coro, which cannot take direct advantage of multiple |
911 |
|
|
CPUs, is often orders of magnitude faster because it shares data using |
912 |
|
|
real threads, refer to my talk for details). |
913 |
|
|
|
914 |
|
|
As summary, i-threads *use* threads to implement processes, while |
915 |
|
|
the compatible forks module *uses* processes to emulate, uhm, |
916 |
|
|
processes. I-threads slow down every perl program when enabled, and |
917 |
|
|
outside of windows, serve no (or little) practical purpose, but |
918 |
|
|
disadvantages every single-threaded Perl program. |
919 |
|
|
|
920 |
|
|
This is the reason that I try to avoid the name "ithreads", as it is |
921 |
|
|
misleading as it implies that it implements some kind of thread model for |
922 |
|
|
perl, and prefer the name "windows process emulation", which describes the |
923 |
|
|
actual use and behaviour of it much better. |
924 |
|
|
|
925 |
root |
1.9 |
=head1 SEE ALSO |
926 |
|
|
|
927 |
root |
1.181 |
Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
928 |
root |
1.152 |
|
929 |
|
|
Debugging: L<Coro::Debug>. |
930 |
|
|
|
931 |
|
|
Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
932 |
root |
1.67 |
|
933 |
root |
1.238 |
Locking and IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
934 |
root |
1.235 |
L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
935 |
root |
1.67 |
|
936 |
root |
1.238 |
I/O and Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
937 |
root |
1.181 |
|
938 |
root |
1.238 |
Compatibility with other modules: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
939 |
root |
1.235 |
a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
940 |
|
|
L<Coro::Select>. |
941 |
root |
1.152 |
|
942 |
root |
1.181 |
XS API: L<Coro::MakeMaker>. |
943 |
root |
1.67 |
|
944 |
root |
1.238 |
Low level Configuration, Thread Environment, Continuations: L<Coro::State>. |
945 |
root |
1.1 |
|
946 |
|
|
=head1 AUTHOR |
947 |
|
|
|
948 |
root |
1.66 |
Marc Lehmann <schmorp@schmorp.de> |
949 |
root |
1.64 |
http://home.schmorp.de/ |
950 |
root |
1.1 |
|
951 |
|
|
=cut |
952 |
|
|
|