Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async coroutine like this:

 sub some_func : Coro {
    # some more async code
 }

 cede;

=head1 DESCRIPTION

This module collection manages coroutines. Coroutines are similar to
threads but don't run in parallel.

In this module, coroutines are defined as "callchain + lexical variables
+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
callchain, it's own set of lexicals and it's own set of perl's most
important global variables.

=cut

package Coro;

use strict;
no warnings "uninitialized";

use Coro::State;

use base qw(Coro::State Exporter);

our $idle;    # idle handler
our $main;    # main coroutine
our $current; # current coroutine

our $VERSION = '3.0';

our @EXPORT = qw(async cede schedule terminate current unblock_sub);
our %EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
our @EXPORT_OK = @{$EXPORT_TAGS{prio}};

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      no strict 'refs';

      Coro->export_to_level(1, @_);

      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
         my ($package, $ref) = (shift, shift);
         my @attrs;
         for (@_) {
            if ($_ eq "Coro") {
               push @async, $ref;
               unless ($init++) {
                  eval q{
                     sub INIT {
                        &async(pop @async) while @async;
                     }
                  };
               }
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

}

=over 4

=item $main

This coroutine represents the main program.

=cut

$main = new Coro;

=item $current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value
is C<$main> (of course).

This variable is B<strictly> I<read-only>. It is provided for performance
reasons. If performance is not essentiel you are encouraged to use the
C<Coro::current> function instead.

=cut

# maybe some other module used Coro::Specific before...
if ($current) {
   $main->{specific} = $current->{specific};
}

$current = $main;

sub current() { $current }

=item $idle

A callback that is called whenever the scheduler finds no ready coroutines
to run. The default implementation prints "FATAL: deadlock detected" and
exits, because the program has no other way to continue.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wake up a
coroutine so the scheduler can run it.

Please note that if your callback recursively invokes perl (e.g. for event
handlers), then it must be prepared to be called recursively.

=cut

$idle = sub {
   print STDERR "FATAL: deadlock detected\n";
   exit (51);
};

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager; $manager = new Coro sub {
   while () {
      # by overwriting the state object with the manager we destroy it
      # while still being able to schedule this coroutine (in case it has
      # been readied multiple times. this is harmless since the manager
      # can be called as many times as neccessary and will always
      # remove itself from the runqueue
      while (@destroy) {
         my $coro = pop @destroy;
         $coro->{status} ||= [];
         $_->ready for @{delete $coro->{join} || []};

         # the next line destroys the coro state, but keeps the
         # coroutine itself intact (we basically make it a zombie
         # coroutine that always runs the manager thread, so it's possible
         # to transfer() to this coroutine).
         $coro->_clone_state_from ($manager);
      }
      &schedule;
   }
};

# static methods. not really.

=back

=head2 STATIC METHODS

Static methods are actually functions that operate on the current coroutine only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous coroutine and return it's coroutine object
(usually unused). When the sub returns the new coroutine is automatically
terminated.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

When the coroutine dies, the program will exit, just as in the main
program.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

=cut

sub async(&@) {
   my $pid = new Coro @_;
   $pid->ready;
   $pid
}

=item schedule

Calls the scheduler. Please note that the current coroutine will not be put
into the ready queue, so calling this function usually means you will
never be called again unless something else (e.g. an event handler) calls
ready.

The canonical way to wait on external events is this:

   {
      # remember current coroutine
      my $current = $Coro::current;

      # register a hypothetical event handler
      on_event_invoke sub {
         # wake up sleeping coroutine
         $current->ready;
         undef $current;
      };

      # call schedule until event occured.
      # in case we are woken up for other reasons
      # (current still defined), loop.
      Coro::schedule while $current;
   }

=item cede

"Cede" to other coroutines. This function puts the current coroutine into the
ready queue and calls C<schedule>, which has the effect of giving up the
current "timeslice" to other coroutines of the same or higher priority.

=item terminate [arg...]

Terminates the current coroutine with the given status values (see L<cancel>).

=cut

sub terminate {
   $current->cancel (@_);
}

=back

# dynamic methods

=head2 COROUTINE METHODS

These are the methods you can call on coroutine objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new coroutine and return it. When the sub returns the coroutine
automatically terminates as if C<terminate> with the returned values were
called. To make the coroutine run you must first put it into the ready queue
by calling the ready method.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

=cut

sub _new_coro {
   terminate &{+shift};
}

sub new {
   my $class = shift;

   $class->SUPER::new (\&_new_coro, @_)
}

=item $success = $coroutine->ready

Put the given coroutine into the ready queue (according to it's priority)
and return true. If the coroutine is already in the ready queue, do nothing
and return false.

=item $is_ready = $coroutine->is_ready

Return wether the coroutine is currently the ready queue or not,

=item $coroutine->cancel (arg...)

Terminates the given coroutine and makes it return the given arguments as
status (default: the empty list).

=cut

sub cancel {
   my $self = shift;
   $self->{status} = [@_];
   push @destroy, $self;
   $manager->ready;
   &schedule if $current == $self;
}

=item $coroutine->join

Wait until the coroutine terminates and return any values given to the
C<terminate> or C<cancel> functions. C<join> can be called multiple times
from multiple coroutine.

=cut

sub join {
   my $self = shift;
   unless ($self->{status}) {
      push @{$self->{join}}, $current;
      &schedule;
   }
   wantarray ? @{$self->{status}} : $self->{status}[0];
}

=item $oldprio = $coroutine->prio ($newprio)

Sets (or gets, if the argument is missing) the priority of the
coroutine. Higher priority coroutines get run before lower priority
coroutines. Priorities are small signed integers (currently -4 .. +3),
that you can refer to using PRIO_xxx constants (use the import tag :prio
to get then):

   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH
   current->prio(PRIO_HIGH);

The idle coroutine ($Coro::idle) always has a lower priority than any
existing coroutine.

Changing the priority of the current coroutine will take effect immediately,
but changing the priority of coroutines in the ready queue (but not
running) will only take effect after the next schedule (of that
coroutine). This is a bug that will be fixed in some future version.

=item $newprio = $coroutine->nice ($change)

Similar to C<prio>, but subtract the given value from the priority (i.e.
higher values mean lower priority, just as in unix).

=item $olddesc = $coroutine->desc ($newdesc)

Sets (or gets in case the argument is missing) the description for this
coroutine. This is just a free-form string you can associate with a coroutine.

=cut

sub desc {
   my $old = $_[0]{desc};
   $_[0]{desc} = $_[1] if @_ > 1;
   $old;
}

=back

=head2 UTILITY FUNCTIONS

=over 4

=item unblock_sub { ... }

This utility function takes a BLOCK or code reference and "unblocks" it,
returning the new coderef. This means that the new coderef will return
immediately without blocking, returning nothing, while the original code
ref will be called (with parameters) from within its own coroutine.

The reason this fucntion exists is that many event libraries (such as the
venerable L<Event|Event> module) are not coroutine-safe (a weaker form
of thread-safety). This means you must not block within event callbacks,
otherwise you might suffer from crashes or worse.

This function allows your callbacks to block by executing them in another
coroutine where it is safe to block. One example where blocking is handy
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
disk.

In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
creating event callbacks that want to block.

=cut

our @unblock_pool;
our @unblock_queue;
our $UNBLOCK_POOL_SIZE = 2;

sub unblock_handler_ {
   while () {
      my ($cb, @arg) = @{ delete $Coro::current->{arg} };
      $cb->(@arg);

      last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
      push @unblock_pool, $Coro::current;
      schedule;
   }        
}           

our $unblock_scheduler = async {
   while () {
      while (my $cb = pop @unblock_queue) {
         my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
         $handler->{arg} = $cb;
         $handler->ready;
         cede;
      }

      schedule;
   }
};

sub unblock_sub(&) {
   my $cb = shift;

   sub {
      push @unblock_queue, [$cb, @_];
      $unblock_scheduler->ready;
   }
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - you must make very sure that no coro is still active on global
   destruction. very bad things might happen otherwise (usually segfaults).

 - this module is not thread-safe. You should only ever use this module
   from the same thread (this requirement might be losened in the future
   to allow per-thread schedulers, but Coro::State does not yet allow
   this).

=head1 SEE ALSO

Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.

Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.

Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.

Embedding: L<Coro:MakeMaker>

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.92
Committed:	Fri Dec 1 03:47:55 2006 UTC (17 years, 5 months ago) by root
Branch:	MAIN
Changes since 1.91:	+99 -38 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.8	Coro - coroutine process abstraction
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8
9	root	1.8	async {
10			# some asynchronous thread of execution
11	root	1.2	};
12
13	root	1.92	# alternatively create an async coroutine like this:
14	root	1.6
15	root	1.8	sub some_func : Coro {
16			# some more async code
17			}
18
19	root	1.22	cede;
20	root	1.2
21	root	1.1	=head1 DESCRIPTION
22
23	root	1.14	This module collection manages coroutines. Coroutines are similar to
24	root	1.42	threads but don't run in parallel.
25	root	1.14
26	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
27	root	1.23	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
28			callchain, it's own set of lexicals and it's own set of perl's most
29			important global variables.
30	root	1.22
31	root	1.8	=cut
32
33			package Coro;
34
35	root	1.71	use strict;
36			no warnings "uninitialized";
37	root	1.36
38	root	1.8	use Coro::State;
39
40	root	1.83	use base qw(Coro::State Exporter);
41	pcg	1.55
42	root	1.83	our $idle; # idle handler
43	root	1.71	our $main; # main coroutine
44			our $current; # current coroutine
45	root	1.8
46	root	1.88	our $VERSION = '3.0';
47	root	1.8
48	root	1.92	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
49	root	1.71	our %EXPORT_TAGS = (
50	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51			);
52	root	1.71	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
53	root	1.8
54			{
55			my @async;
56	root	1.26	my $init;
57	root	1.8
58			# this way of handling attributes simply is NOT scalable ;()
59			sub import {
60	root	1.71	no strict 'refs';
61
62	root	1.8	Coro->export_to_level(1, @_);
63	root	1.71
64	root	1.8	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66			my ($package, $ref) = (shift, shift);
67			my @attrs;
68			for (@_) {
69			if ($_ eq "Coro") {
70			push @async, $ref;
71	root	1.26	unless ($init++) {
72			eval q{
73			sub INIT {
74			&async(pop @async) while @async;
75			}
76			};
77			}
78	root	1.8	} else {
79	root	1.17	push @attrs, $_;
80	root	1.8	}
81			}
82	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	root	1.8	};
84			}
85
86			}
87
88	root	1.43	=over 4
89
90	root	1.8	=item $main
91	root	1.2
92	root	1.8	This coroutine represents the main program.
93	root	1.1
94			=cut
95
96	pcg	1.55	$main = new Coro;
97	root	1.8
98	root	1.19	=item $current (or as function: current)
99	root	1.1
100	root	1.83	The current coroutine (the last coroutine switched to). The initial value
101			is C<$main> (of course).
102
103			This variable is B<strictly> I<read-only>. It is provided for performance
104			reasons. If performance is not essentiel you are encouraged to use the
105			C<Coro::current> function instead.
106	root	1.1
107	root	1.8	=cut
108
109			# maybe some other module used Coro::Specific before...
110			if ($current) {
111			$main->{specific} = $current->{specific};
112	root	1.1	}
113
114	pcg	1.55	$current = $main;
115	root	1.19
116			sub current() { $current }
117	root	1.9
118			=item $idle
119
120	root	1.83	A callback that is called whenever the scheduler finds no ready coroutines
121			to run. The default implementation prints "FATAL: deadlock detected" and
122	root	1.91	exits, because the program has no other way to continue.
123	root	1.83
124			This hook is overwritten by modules such as C<Coro::Timer> and
125	root	1.91	C<Coro::Event> to wait on an external event that hopefully wake up a
126			coroutine so the scheduler can run it.
127
128			Please note that if your callback recursively invokes perl (e.g. for event
129			handlers), then it must be prepared to be called recursively.
130	root	1.9
131			=cut
132
133	root	1.83	$idle = sub {
134	root	1.9	print STDERR "FATAL: deadlock detected\n";
135	root	1.83	exit (51);
136	root	1.9	};
137	root	1.8
138	root	1.24	# this coroutine is necessary because a coroutine
139			# cannot destroy itself.
140			my @destroy;
141	root	1.86	my $manager; $manager = new Coro sub {
142	pcg	1.57	while () {
143	root	1.37	# by overwriting the state object with the manager we destroy it
144			# while still being able to schedule this coroutine (in case it has
145			# been readied multiple times. this is harmless since the manager
146			# can be called as many times as neccessary and will always
147			# remove itself from the runqueue
148	root	1.40	while (@destroy) {
149			my $coro = pop @destroy;
150			$coro->{status} \|\|= [];
151			$_->ready for @{delete $coro->{join} \|\| []};
152	pcg	1.59
153	root	1.83	# the next line destroys the coro state, but keeps the
154	root	1.92	# coroutine itself intact (we basically make it a zombie
155			# coroutine that always runs the manager thread, so it's possible
156			# to transfer() to this coroutine).
157	root	1.83	$coro->_clone_state_from ($manager);
158	root	1.40	}
159	root	1.24	&schedule;
160			}
161			};
162
163	root	1.8	# static methods. not really.
164	root	1.43
165			=back
166	root	1.8
167			=head2 STATIC METHODS
168
169	root	1.92	Static methods are actually functions that operate on the current coroutine only.
170	root	1.8
171			=over 4
172
173	root	1.13	=item async { ... } [@args...]
174	root	1.8
175	root	1.92	Create a new asynchronous coroutine and return it's coroutine object
176			(usually unused). When the sub returns the new coroutine is automatically
177	root	1.8	terminated.
178
179	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
180
181	root	1.79	When the coroutine dies, the program will exit, just as in the main
182			program.
183
184	root	1.13	# create a new coroutine that just prints its arguments
185			async {
186			print "@_\n";
187			} 1,2,3,4;
188
189	root	1.8	=cut
190
191	root	1.13	sub async(&@) {
192			my $pid = new Coro @_;
193	root	1.11	$pid->ready;
194	root	1.85	$pid
195	root	1.8	}
196	root	1.1
197	root	1.8	=item schedule
198	root	1.6
199	root	1.92	Calls the scheduler. Please note that the current coroutine will not be put
200	root	1.8	into the ready queue, so calling this function usually means you will
201	root	1.91	never be called again unless something else (e.g. an event handler) calls
202			ready.
203
204			The canonical way to wait on external events is this:
205
206			{
207	root	1.92	# remember current coroutine
208	root	1.91	my $current = $Coro::current;
209
210			# register a hypothetical event handler
211			on_event_invoke sub {
212			# wake up sleeping coroutine
213			$current->ready;
214			undef $current;
215			};
216
217			# call schedule until event occured.
218			# in case we are woken up for other reasons
219			# (current still defined), loop.
220			Coro::schedule while $current;
221			}
222	root	1.1
223	root	1.22	=item cede
224	root	1.1
225	root	1.92	"Cede" to other coroutines. This function puts the current coroutine into the
226	root	1.22	ready queue and calls C<schedule>, which has the effect of giving up the
227			current "timeslice" to other coroutines of the same or higher priority.
228	root	1.7
229	root	1.40	=item terminate [arg...]
230	root	1.7
231	root	1.92	Terminates the current coroutine with the given status values (see L<cancel>).
232	root	1.13
233	root	1.1	=cut
234
235	root	1.8	sub terminate {
236	pcg	1.59	$current->cancel (@_);
237	root	1.1	}
238	root	1.6
239	root	1.8	=back
240
241			# dynamic methods
242
243	root	1.92	=head2 COROUTINE METHODS
244	root	1.8
245	root	1.92	These are the methods you can call on coroutine objects.
246	root	1.6
247	root	1.8	=over 4
248
249	root	1.13	=item new Coro \&sub [, @args...]
250	root	1.8
251	root	1.92	Create a new coroutine and return it. When the sub returns the coroutine
252	root	1.40	automatically terminates as if C<terminate> with the returned values were
253	root	1.92	called. To make the coroutine run you must first put it into the ready queue
254	root	1.41	by calling the ready method.
255	root	1.13
256	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
257
258	root	1.6	=cut
259
260	root	1.84	sub _new_coro {
261	root	1.13	terminate &{+shift};
262			}
263
264	root	1.8	sub new {
265			my $class = shift;
266	root	1.83
267	root	1.84	$class->SUPER::new (\&_new_coro, @_)
268	root	1.8	}
269	root	1.6
270	root	1.92	=item $success = $coroutine->ready
271	root	1.1
272	root	1.92	Put the given coroutine into the ready queue (according to it's priority)
273			and return true. If the coroutine is already in the ready queue, do nothing
274	root	1.90	and return false.
275	root	1.1
276	root	1.92	=item $is_ready = $coroutine->is_ready
277	root	1.90
278	root	1.92	Return wether the coroutine is currently the ready queue or not,
279	root	1.28
280	root	1.92	=item $coroutine->cancel (arg...)
281	root	1.28
282	root	1.92	Terminates the given coroutine and makes it return the given arguments as
283	pcg	1.59	status (default: the empty list).
284	root	1.28
285			=cut
286
287			sub cancel {
288	pcg	1.59	my $self = shift;
289			$self->{status} = [@_];
290			push @destroy, $self;
291	root	1.28	$manager->ready;
292	pcg	1.59	&schedule if $current == $self;
293	root	1.40	}
294
295	root	1.92	=item $coroutine->join
296	root	1.40
297			Wait until the coroutine terminates and return any values given to the
298	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
299	root	1.92	from multiple coroutine.
300	root	1.40
301			=cut
302
303			sub join {
304			my $self = shift;
305			unless ($self->{status}) {
306			push @{$self->{join}}, $current;
307			&schedule;
308			}
309			wantarray ? @{$self->{status}} : $self->{status}[0];
310	root	1.31	}
311
312	root	1.92	=item $oldprio = $coroutine->prio ($newprio)
313	root	1.31
314	root	1.41	Sets (or gets, if the argument is missing) the priority of the
315	root	1.92	coroutine. Higher priority coroutines get run before lower priority
316			coroutines. Priorities are small signed integers (currently -4 .. +3),
317	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
318			to get then):
319	root	1.31
320			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
321			3 > 1 > 0 > -1 > -3 > -4
322
323			# set priority to HIGH
324			current->prio(PRIO_HIGH);
325
326			The idle coroutine ($Coro::idle) always has a lower priority than any
327			existing coroutine.
328
329	root	1.92	Changing the priority of the current coroutine will take effect immediately,
330			but changing the priority of coroutines in the ready queue (but not
331	root	1.31	running) will only take effect after the next schedule (of that
332	root	1.92	coroutine). This is a bug that will be fixed in some future version.
333	root	1.31
334	root	1.92	=item $newprio = $coroutine->nice ($change)
335	root	1.31
336			Similar to C<prio>, but subtract the given value from the priority (i.e.
337			higher values mean lower priority, just as in unix).
338
339	root	1.92	=item $olddesc = $coroutine->desc ($newdesc)
340	root	1.41
341			Sets (or gets in case the argument is missing) the description for this
342	root	1.92	coroutine. This is just a free-form string you can associate with a coroutine.
343	root	1.41
344			=cut
345
346			sub desc {
347			my $old = $_[0]{desc};
348			$_[0]{desc} = $_[1] if @_ > 1;
349			$old;
350	root	1.8	}
351	root	1.1
352	root	1.8	=back
353	root	1.2
354	root	1.92	=head2 UTILITY FUNCTIONS
355
356			=over 4
357
358			=item unblock_sub { ... }
359
360			This utility function takes a BLOCK or code reference and "unblocks" it,
361			returning the new coderef. This means that the new coderef will return
362			immediately without blocking, returning nothing, while the original code
363			ref will be called (with parameters) from within its own coroutine.
364
365			The reason this fucntion exists is that many event libraries (such as the
366			venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
367			of thread-safety). This means you must not block within event callbacks,
368			otherwise you might suffer from crashes or worse.
369
370			This function allows your callbacks to block by executing them in another
371			coroutine where it is safe to block. One example where blocking is handy
372			is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
373			disk.
374
375			In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
376			creating event callbacks that want to block.
377
378			=cut
379
380			our @unblock_pool;
381			our @unblock_queue;
382			our $UNBLOCK_POOL_SIZE = 2;
383
384			sub unblock_handler_ {
385			while () {
386			my ($cb, @arg) = @{ delete $Coro::current->{arg} };
387			$cb->(@arg);
388
389			last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
390			push @unblock_pool, $Coro::current;
391			schedule;
392			}
393			}
394
395			our $unblock_scheduler = async {
396			while () {
397			while (my $cb = pop @unblock_queue) {
398			my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
399			$handler->{arg} = $cb;
400			$handler->ready;
401			cede;
402			}
403
404			schedule;
405			}
406			};
407
408			sub unblock_sub(&) {
409			my $cb = shift;
410
411			sub {
412			push @unblock_queue, [$cb, @_];
413			$unblock_scheduler->ready;
414			}
415			}
416
417			=back
418
419	root	1.8	=cut
420	root	1.2
421	root	1.8	1;
422	root	1.14
423	root	1.17	=head1 BUGS/LIMITATIONS
424	root	1.14
425	root	1.52	- you must make very sure that no coro is still active on global
426	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
427	root	1.52
428			- this module is not thread-safe. You should only ever use this module
429			from the same thread (this requirement might be losened in the future
430			to allow per-thread schedulers, but Coro::State does not yet allow
431			this).
432	root	1.9
433			=head1 SEE ALSO
434
435	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
436
437			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
438
439			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
440
441			Embedding: L<Coro:MakeMaker>
442	root	1.1
443			=head1 AUTHOR
444
445	root	1.66	Marc Lehmann <schmorp@schmorp.de>
446	root	1.64	http://home.schmorp.de/
447	root	1.1
448			=cut
449