--- Coro/Coro.pm 2008/10/04 23:26:30 1.204 +++ Coro/Coro.pm 2009/06/17 21:38:23 1.256 @@ -1,6 +1,6 @@ =head1 NAME -Coro - coroutine process abstraction +Coro - the only real threads in perl =head1 SYNOPSIS @@ -13,7 +13,7 @@ print "4\n"; }; print "1\n"; - cede; # yield to coroutine + cede; # yield to coro print "3\n"; cede; # and again @@ -28,48 +28,61 @@ =head1 DESCRIPTION -This module collection manages coroutines. Coroutines are similar to -threads but don't (in general) run in parallel at the same time even -on SMP machines. The specific flavor of coroutine used in this module -also guarantees you that it will not switch between coroutines unless -necessary, at easily-identified points in your program, so locking and -parallel access are rarely an issue, making coroutine programming much -safer and easier than threads programming. - -Unlike a normal perl program, however, coroutines allow you to have -multiple running interpreters that share data, which is especially useful -to code pseudo-parallel processes and for event-based programming, such as -multiple HTTP-GET requests running concurrently. See L to -learn more. - -Coroutines are also useful because Perl has no support for threads (the so -called "threads" that perl offers are nothing more than the (bad) process -emulation coming from the Windows platform: On standard operating systems -they serve no purpose whatsoever, except by making your programs slow and -making them use a lot of memory. Best disable them when building perl, or -aks your software vendor/distributor to do it for you). +For a tutorial-style introduction, please read the L +manpage. This manpage mainly contains reference information. -In this module, coroutines are defined as "callchain + lexical variables + -@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain, +This module collection manages continuations in general, most often in +the form of cooperative threads (also called coros, or simply "coro" +in the documentation). They are similar to kernel threads but don't (in +general) run in parallel at the same time even on SMP machines. The +specific flavor of thread offered by this module also guarantees you that +it will not switch between threads unless necessary, at easily-identified +points in your program, so locking and parallel access are rarely an +issue, making thread programming much safer and easier than using other +thread models. + +Unlike the so-called "Perl threads" (which are not actually real threads +but only the windows process emulation ported to unix, and as such act +as processes), Coro provides a full shared address space, which makes +communication between threads very easy. And Coro's threads are fast, +too: disabling the Windows process emulation code in your perl and using +Coro can easily result in a two to four times speed increase for your +programs. A parallel matrix multiplication benchmark runs over 300 times +faster on a single core than perl's pseudo-threads on a quad core using +all four cores. + +Coro achieves that by supporting multiple running interpreters that share +data, which is especially useful to code pseudo-parallel processes and +for event-based programming, such as multiple HTTP-GET requests running +concurrently. See L to learn more on how to integrate Coro +into an event-based environment. + +In this module, a thread is defined as "callchain + lexical variables + +some package variables + C stack), that is, a thread has its own callchain, its own set of lexicals and its own set of perls most important global -variables (see L for more configuration). +variables (see L for more configuration and background info). + +See also the C section at the end of this document - the Coro +module family is quite large. =cut package Coro; -use strict; +use strict qw(vars subs); no warnings "uninitialized"; +use Guard (); + use Coro::State; use base qw(Coro::State Exporter); our $idle; # idle handler -our $main; # main coroutine -our $current; # current coroutine +our $main; # main coro +our $current; # current coro -our $VERSION = 4.8; +our $VERSION = 5.132; our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); our %EXPORT_TAGS = ( @@ -77,60 +90,61 @@ ); our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); +=head1 GLOBAL VARIABLES + =over 4 =item $Coro::main -This variable stores the coroutine object that represents the main +This variable stores the Coro object that represents the main program. While you cna C it and do most other things you can do to -coroutines, it is mainly useful to compare again C<$Coro::current>, to see +coro, it is mainly useful to compare again C<$Coro::current>, to see whether you are running in the main program or not. =cut -$main = new Coro; +# $main is now being initialised by Coro::State =item $Coro::current -The coroutine object representing the current coroutine (the last -coroutine that the Coro scheduler switched to). The initial value is -C<$main> (of course). +The Coro object representing the current coro (the last +coro that the Coro scheduler switched to). The initial value is +C<$Coro::main> (of course). This variable is B I. You can take copies of the -value stored in it and use it as any other coroutine object, but you must +value stored in it and use it as any other Coro object, but you must not otherwise modify the variable itself. =cut -$main->{desc} = "[main::]"; - -# maybe some other module used Coro::Specific before... -$main->{_specific} = $current->{_specific} - if $current; - -_set_current $main; - sub current() { $current } # [DEPRECATED] =item $Coro::idle This variable is mainly useful to integrate Coro into event loops. It is -usually better to rely on L or LC, as this is +usually better to rely on L or L, as this is pretty low-level functionality. -This variable stores a callback that is called whenever the scheduler -finds no ready coroutines to run. The default implementation prints -"FATAL: deadlock detected" and exits, because the program has no other way -to continue. +This variable stores either a Coro object or a callback. -This hook is overwritten by modules such as C and +If it is a callback, the it is called whenever the scheduler finds no +ready coros to run. The default implementation prints "FATAL: +deadlock detected" and exits, because the program has no other way to +continue. + +If it is a coro object, then this object will be readied (without +invoking any ready hooks, however) when the scheduler finds no other ready +coros to run. + +This hook is overwritten by modules such as C and C to wait on an external event that hopefully wake up a -coroutine so the scheduler can run it. +coro so the scheduler can run it. Note that the callback I, under any circumstances, block -the current coroutine. Normally, this is achieved by having an "idle -coroutine" that calls the event loop and then blocks again, and then -readying that coroutine in the idle handler. +the current coro. Normally, this is achieved by having an "idle +coro" that calls the event loop and then blocks again, and then +readying that coro in the idle handler, or by simply placing the idle +coro in this variable. See L or L for examples of using this technique. @@ -145,63 +159,51 @@ Carp::croak ("FATAL: deadlock detected"); }; -sub _cancel { - my ($self) = @_; - - # free coroutine data and mark as destructed - $self->_destroy - or return; - - # call all destruction callbacks - $_->(@{$self->{_status}}) - for @{(delete $self->{_on_destroy}) || []}; -} - -# this coroutine is necessary because a coroutine +# this coro is necessary because a coro # cannot destroy itself. -my @destroy; -my $manager; +our @destroy; +our $manager; $manager = new Coro sub { while () { - (shift @destroy)->_cancel + Coro::State::cancel shift @destroy while @destroy; &schedule; } }; -$manager->desc ("[coro manager]"); +$manager->{desc} = "[coro manager]"; $manager->prio (PRIO_MAX); =back -=head2 SIMPLE COROUTINE CREATION +=head1 SIMPLE CORO CREATION =over 4 =item async { ... } [@args...] -Create a new coroutine and return it's coroutine object (usually -unused). The coroutine will be put into the ready queue, so +Create a new coro and return its Coro object (usually +unused). The coro will be put into the ready queue, so it will start running automatically on the next scheduler run. The first argument is a codeblock/closure that should be executed in the -coroutine. When it returns argument returns the coroutine is automatically +coro. When it returns argument returns the coro is automatically terminated. The remaining arguments are passed as arguments to the closure. -See the C constructor for info about the coroutine -environment in which coroutines are executed. +See the C constructor for info about the coro +environment in which coro are executed. -Calling C in a coroutine will do the same as calling exit outside -the coroutine. Likewise, when the coroutine dies, the program will exit, +Calling C in a coro will do the same as calling exit outside +the coro. Likewise, when the coro dies, the program will exit, just as it would in the main program. If you do not want that, you can provide a default C handler, or simply avoid dieing (by use of C). -Example: Create a new coroutine that just prints its arguments. +Example: Create a new coro that just prints its arguments. async { print "@_\n"; @@ -217,129 +219,93 @@ =item async_pool { ... } [@args...] -Similar to C, but uses a coroutine pool, so you should not call +Similar to C, but uses a coro pool, so you should not call terminate or join on it (although you are allowed to), and you get a -coroutine that might have executed other code already (which can be good +coro that might have executed other code already (which can be good or bad :). -On the plus side, this function is faster than creating (and destroying) -a completly new coroutine, so if you need a lot of generic coroutines in -quick successsion, use C, not C. +On the plus side, this function is about twice as fast as creating (and +destroying) a completely new coro, so if you need a lot of generic +coros in quick successsion, use C, not C. The code block is executed in an C context and a warning will be issued in case of an exception instead of terminating the program, as -C does. As the coroutine is being reused, stuff like C +C does. As the coro is being reused, stuff like C will not work in the expected way, unless you call terminate or cancel, which somehow defeats the purpose of pooling (but is fine in the exceptional case). The priority will be reset to C<0> after each run, tracing will be disabled, the description will be reset and the default output filehandle -gets restored, so you can change all these. Otherwise the coroutine will -be re-used "as-is": most notably if you change other per-coroutine global +gets restored, so you can change all these. Otherwise the coro will +be re-used "as-is": most notably if you change other per-coro global stuff such as C<$/> you I revert that change, which is most simply done by using local as in: C<< local $/ >>. -The idle pool size is limited to C<8> idle coroutines (this can be +The idle pool size is limited to C<8> idle coros (this can be adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle coros as required. -If you are concerned about pooled coroutines growing a lot because a +If you are concerned about pooled coros growing a lot because a single C used a lot of stackspace you can e.g. C once per second or so to slowly replenish the pool. In -addition to that, when the stacks used by a handler grows larger than 16kb +addition to that, when the stacks used by a handler grows larger than 32kb (adjustable via $Coro::POOL_RSS) it will also be destroyed. =cut our $POOL_SIZE = 8; -our $POOL_RSS = 16 * 1024; +our $POOL_RSS = 32 * 1024; our @async_pool; sub pool_handler { - my $cb; - while () { eval { - while () { - _pool_1 $cb; - &$cb; - _pool_2 $cb; - &schedule; - } + &{&_pool_handler} while 1; }; - if ($@) { - last if $@ eq "\3async_pool terminate\2\n"; - warn $@; - } + warn $@ if $@; } } -sub async_pool(&@) { - # this is also inlined into the unlock_scheduler - my $coro = (pop @async_pool) || new Coro \&pool_handler; - - $coro->{_invoke} = [@_]; - $coro->ready; - - $coro -} - =back -=head2 STATIC METHODS +=head1 STATIC METHODS -Static methods are actually functions that operate on the current coroutine. +Static methods are actually functions that implicitly operate on the +current coro. =over 4 =item schedule -Calls the scheduler. The scheduler will find the next coroutine that is -to be run from the ready queue and switches to it. The next coroutine +Calls the scheduler. The scheduler will find the next coro that is +to be run from the ready queue and switches to it. The next coro to be run is simply the one with the highest priority that is longest -in its ready queue. If there is no coroutine ready, it will clal the +in its ready queue. If there is no coro ready, it will clal the C<$Coro::idle> hook. -Please note that the current coroutine will I be put into the ready +Please note that the current coro will I 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 C<< ->ready >>, thus waking you up. This makes C I generic method to use to block the current -coroutine and wait for events: first you remember the current coroutine in +coro and wait for events: first you remember the current coro in a variable, then arrange for some callback of yours to call C<< ->ready >> on that once some event happens, and last you call C to put -yourself to sleep. Note that a lot of things can wake your coroutine up, +yourself to sleep. Note that a lot of things can wake your coro up, so you need to check whether the event indeed happened, e.g. by storing the status in a variable. -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 occurred. - # in case we are woken up for other reasons - # (current still defined), loop. - Coro::schedule while $current; - } +See B, below, for some ways to wait for callbacks. =item cede -"Cede" to other coroutines. This function puts the current coroutine into +"Cede" to other coros. This function puts the current coro into the ready queue and calls C, which has the effect of giving -up the current "timeslice" to other coroutines of the same or higher -priority. Once your coroutine gets its turn again it will automatically be +up the current "timeslice" to other coros of the same or higher +priority. Once your coro gets its turn again it will automatically be resumed. This function is often called C in other languages. @@ -347,29 +313,110 @@ =item Coro::cede_notself Works like cede, but is not exported by default and will cede to I -coroutine, regardless of priority. This is useful sometimes to ensure +coro, regardless of priority. This is useful sometimes to ensure progress is made. =item terminate [arg...] -Terminates the current coroutine with the given status values (see L). +Terminates the current coro with the given status values (see L). + +=item Coro::on_enter BLOCK, Coro::on_leave BLOCK + +These function install enter and leave winders in the current scope. The +enter block will be executed when on_enter is called and whenever the +current coro is re-entered by the scheduler, while the leave block is +executed whenever the current coro is blocked by the scheduler, and +also when the containing scope is exited (by whatever means, be it exit, +die, last etc.). + +I. That means: do not even think about calling C without an +eval, and do not even think of entering the scheduler in any way. + +Since both BLOCKs are tied to the current scope, they will automatically +be removed when the current scope exits. + +These functions implement the same concept as C in scheme +does, and are useful when you want to localise some resource to a specific +coro. + +They slow down thread switching considerably for coros that use them +(about 40% for a BLOCK with a single assignment, so thread switching is +still reasonably fast if the handlers are fast). + +These functions are best understood by an example: The following function +will change the current timezone to "Antarctica/South_Pole", which +requires a call to C, but by using C and C, +which remember/change the current timezone and restore the previous +value, respectively, the timezone is only changed for the coro that +installed those handlers. + + use POSIX qw(tzset); + + async { + my $old_tz; # store outside TZ value here + + Coro::on_enter { + $old_tz = $ENV{TZ}; # remember the old value + + $ENV{TZ} = "Antarctica/South_Pole"; + tzset; # enable new value + }; + + Coro::on_leave { + $ENV{TZ} = $old_tz; + tzset; # restore old value + }; + + # at this place, the timezone is Antarctica/South_Pole, + # without disturbing the TZ of any other coro. + }; + +This can be used to localise about any resource (locale, uid, current +working directory etc.) to a block, despite the existance of other +coros. + +Another interesting example implements time-sliced multitasking using +interval timers (this could obviously be optimised, but does the job): + + # "timeslice" the given block + sub timeslice(&) { + use Time::HiRes (); + + Coro::on_enter { + # on entering the thread, we set an VTALRM handler to cede + $SIG{VTALRM} = sub { cede }; + # and then start the interval timer + Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0.01, 0.01; + }; + Coro::on_leave { + # on leaving the thread, we stop the interval timer again + Time::HiRes::setitimer &Time::HiRes::ITIMER_VIRTUAL, 0, 0; + }; + + &{+shift}; + } + + # use like this: + timeslice { + # The following is an endless loop that would normally + # monopolise the process. Since it runs in a timesliced + # environment, it will regularly cede to other threads. + while () { } + }; + =item killall -Kills/terminates/cancels all coroutines except the currently running -one. This is useful after a fork, either in the child or the parent, as -usually only one of them should inherit the running coroutines. +Kills/terminates/cancels all coros except the currently running one. -Note that while this will try to free some of the main programs resources, -you cannot free all of them, so if a coroutine that is not the main -program calls this function, there will be some one-time resource leak. +Note that while this will try to free some of the main interpreter +resources if the calling coro isn't the main coro, but one +cannot free all of them, so if a coro that is not the main coro +calls this function, there will be some one-time resource leak. =cut -sub terminate { - $current->cancel (@_); -} - sub killall { for (Coro::State::list) { $_->cancel @@ -379,76 +426,147 @@ =back -=head2 COROUTINE METHODS +=head1 CORO OBJECT METHODS -These are the methods you can call on coroutine objects (or to create +These are the methods you can call on coro objects (or to create them). =over 4 =item new Coro \&sub [, @args...] -Create a new coroutine and return it. When the sub returns, the coroutine +Create a new coro and return it. When the sub returns, the coro automatically terminates as if C with the returned values were -called. To make the coroutine run you must first put it into the ready +called. To make the coro run you must first put it into the ready queue by calling the ready method. See C and C for additional info about the -coroutine environment. +coro environment. =cut -sub _run_coro { +sub _coro_run { terminate &{+shift}; } -sub new { - my $class = shift; - - $class->SUPER::new (\&_run_coro, @_) -} +=item $success = $coro->ready -=item $success = $coroutine->ready - -Put the given coroutine into the end of its ready queue (there is one -queue for each priority) and return true. If the coroutine is already in +Put the given coro into the end of its ready queue (there is one +queue for each priority) and return true. If the coro is already in the ready queue, do nothing and return false. -This ensures that the scheduler will resume this coroutine automatically -once all the coroutines of higher priority and all coroutines of the same +This ensures that the scheduler will resume this coro automatically +once all the coro of higher priority and all coro of the same priority that were put into the ready queue earlier have been resumed. -=item $is_ready = $coroutine->is_ready +=item $coro->suspend + +Suspends the specified coro. A suspended coro works just like any other +coro, except that the scheduler will not select a suspended coro for +execution. + +Suspending a coro can be useful when you want to keep the coro from +running, but you don't want to destroy it, or when you want to temporarily +freeze a coro (e.g. for debugging) to resume it later. + +A scenario for the former would be to suspend all (other) coros after a +fork and keep them alive, so their destructors aren't called, but new +coros can be created. + +=item $coro->resume + +If the specified coro was suspended, it will be resumed. Note that when +the coro was in the ready queue when it was suspended, it might have been +unreadied by the scheduler, so an activation might have been lost. + +To avoid this, it is best to put a suspended coro into the ready queue +unconditionally, as every synchronisation mechanism must protect itself +against spurious wakeups, and the one in the Coro family certainly do +that. + +=item $is_ready = $coro->is_ready -Return whether the coroutine is currently the ready queue or not, +Returns true iff the Coro object is in the ready queue. Unless the Coro +object gets destroyed, it will eventually be scheduled by the scheduler. -=item $coroutine->cancel (arg...) +=item $is_running = $coro->is_running -Terminates the given coroutine and makes it return the given arguments as -status (default: the empty list). Never returns if the coroutine is the -current coroutine. +Returns true iff the Coro object is currently running. Only one Coro object +can ever be in the running state (but it currently is possible to have +multiple running Coro::States). + +=item $is_suspended = $coro->is_suspended + +Returns true iff this Coro object has been suspended. Suspended Coros will +not ever be scheduled. + +=item $coro->cancel (arg...) + +Terminates the given Coro and makes it return the given arguments as +status (default: the empty list). Never returns if the Coro is the +current Coro. =cut sub cancel { my $self = shift; - $self->{_status} = [@_]; if ($current == $self) { - push @destroy, $self; - $manager->ready; - &schedule while 1; + terminate @_; } else { - $self->_cancel; + $self->{_status} = [@_]; + Coro::State::cancel $self; } } -=item $coroutine->join +=item $coro->schedule_to + +Puts the current coro to sleep (like C), but instead +of continuing with the next coro from the ready queue, always switch to +the given coro object (regardless of priority etc.). The readyness +state of that coro isn't changed. + +This is an advanced method for special cases - I'd love to hear about any +uses for this one. + +=item $coro->cede_to + +Like C, but puts the current coro into the ready +queue. This has the effect of temporarily switching to the given +coro, and continuing some time later. -Wait until the coroutine terminates and return any values given to the +This is an advanced method for special cases - I'd love to hear about any +uses for this one. + +=item $coro->throw ([$scalar]) + +If C<$throw> is specified and defined, it will be thrown as an exception +inside the coro at the next convenient point in time. Otherwise +clears the exception object. + +Coro will check for the exception each time a schedule-like-function +returns, i.e. after each C, C, C<< Coro::Semaphore->down +>>, C<< Coro::Handle->readable >> and so on. Most of these functions +detect this case and return early in case an exception is pending. + +The exception object will be thrown "as is" with the specified scalar in +C<$@>, i.e. if it is a string, no line number or newline will be appended +(unlike with C). + +This can be used as a softer means than C to ask a coro to +end itself, although there is no guarantee that the exception will lead to +termination, and if the exception isn't caught it might well end the whole +program. + +You might also think of C as being the moral equivalent of +Cing a coro with a signal (in this case, a scalar). + +=item $coro->join + +Wait until the coro terminates and return any values given to the C or C functions. C can be called concurrently -from multiple coroutines, and all will be resumed and given the status -return once the C<$coroutine> terminates. +from multiple coro, and all will be resumed and given the status +return once the C<$coro> terminates. =cut @@ -469,9 +587,9 @@ wantarray ? @{$self->{_status}} : $self->{_status}[0]; } -=item $coroutine->on_destroy (\&cb) +=item $coro->on_destroy (\&cb) -Registers a callback that is called when this coroutine gets destroyed, +Registers a callback that is called when this coro gets destroyed, but before it is joined. The callback gets passed the terminate arguments, if any, and I die, under any circumstances. @@ -483,11 +601,11 @@ push @{ $self->{_on_destroy} }, $cb; } -=item $oldprio = $coroutine->prio ($newprio) +=item $oldprio = $coro->prio ($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), +coro. Higher priority coro get run before lower priority +coro. 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): @@ -495,44 +613,29 @@ 3 > 1 > 0 > -1 > -3 > -4 # set priority to HIGH - current->prio(PRIO_HIGH); + current->prio (PRIO_HIGH); -The idle coroutine ($Coro::idle) always has a lower priority than any -existing coroutine. +The idle coro ($Coro::idle) always has a lower priority than any +existing coro. -Changing the priority of the current coroutine will take effect immediately, -but changing the priority of coroutines in the ready queue (but not +Changing the priority of the current coro will take effect immediately, +but changing the priority of coro 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. +coro). This is a bug that will be fixed in some future version. -=item $newprio = $coroutine->nice ($change) +=item $newprio = $coro->nice ($change) Similar to C, but subtract the given value from the priority (i.e. higher values mean lower priority, just as in unix). -=item $olddesc = $coroutine->desc ($newdesc) +=item $olddesc = $coro->desc ($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. - -This method simply sets the C<< $coroutine->{desc} >> member to the given string. You -can modify this member directly if you wish. +coro. This is just a free-form string you can associate with a +coro. -=item $coroutine->throw ([$scalar]) - -If C<$throw> is specified and defined, it will be thrown as an exception -inside the coroutine at the next convinient point in time (usually after -it gains control at the next schedule/transfer/cede). Otherwise clears the -exception object. - -The exception object will be thrown "as is" with the specified scalar in -C<$@>, i.e. if it is a string, no line number or newline will be appended -(unlike with C). - -This can be used as a softer means than C to ask a coroutine to -end itself, although there is no guarentee that the exception will lead to -termination, and if the exception isn't caught it might well end the whole -program. +This method simply sets the C<< $coro->{desc} >> member to the given +string. You can modify this member directly if you wish. =cut @@ -542,54 +645,34 @@ $old; } +sub transfer { + require Carp; + Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); +} + =back -=head2 GLOBAL FUNCTIONS +=head1 GLOBAL FUNCTIONS =over 4 =item Coro::nready -Returns the number of coroutines that are currently in the ready state, +Returns the number of coro that are currently in the ready state, i.e. that can be switched to by calling C directory or -indirectly. The value C<0> means that the only runnable coroutine is the +indirectly. The value C<0> means that the only runnable coro is the currently running one, so C would have no effect, and C would cause a deadlock unless there is an idle handler that wakes up some -coroutines. +coro. =item my $guard = Coro::guard { ... } -This creates and returns a guard object. Nothing happens until the object -gets destroyed, in which case the codeblock given as argument will be -executed. This is useful to free locks or other resources in case of a -runtime error or when the coroutine gets canceled, as in both cases the -guard block will be executed. The guard object supports only one method, -C<< ->cancel >>, which will keep the codeblock from being executed. - -Example: set some flag and clear it again when the coroutine gets canceled -or the function returns: - - sub do_something { - my $guard = Coro::guard { $busy = 0 }; - $busy = 1; - - # do something that requires $busy to be true - } +This function still exists, but is deprecated. Please use the +C function instead. =cut -sub guard(&) { - bless \(my $cb = $_[0]), "Coro::guard" -} - -sub Coro::guard::cancel { - ${$_[0]} = sub { }; -} - -sub Coro::guard::DESTROY { - ${$_[0]}->(); -} - +BEGIN { *guard = \&Guard::guard } =item unblock_sub { ... } @@ -597,16 +680,16 @@ returning a new coderef. Unblocking means that calling the new coderef will return immediately without blocking, returning nothing, while the original code ref will be called (with parameters) from within another -coroutine. +coro. The reason this function exists is that many event libraries (such as the -venerable L module) are not coroutine-safe (a weaker form -of thread-safety). This means you must not block within event callbacks, +venerable L module) are not thread-safe (a weaker form +of reentrancy). This means you must not block within event callbacks, otherwise you might suffer from crashes or worse. The only event library currently known that is safe to use without C is L. 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 +coro where it is safe to block. One example where blocking is handy is when you use the L functions to save results to disk, for example. @@ -614,8 +697,8 @@ creating event callbacks that want to block. If your handler does not plan to block (e.g. simply sends a message to -another coroutine, or puts some other coroutine into the ready queue), -there is no reason to use C. +another coro, or puts some other coro into the ready queue), there is +no reason to use C. Note that you also need to use C for any other callbacks that are indirectly executed by any C-based event loop. For example, when you @@ -634,17 +717,17 @@ our $unblock_scheduler = new Coro sub { while () { while (my $cb = pop @unblock_queue) { - # this is an inlined copy of async_pool - my $coro = (pop @async_pool) || new Coro \&pool_handler; + &async_pool (@$cb); - $coro->{_invoke} = $cb; - $coro->ready; - cede; # for short-lived callbacks, this reduces pressure on the coro pool + # for short-lived callbacks, this reduces pressure on the coro pool + # as the chance is very high that the async_poll coro will be back + # in the idle state when cede returns + cede; } schedule; # sleep well } }; -$unblock_scheduler->desc ("[unblock_sub scheduler]"); +$unblock_scheduler->{desc} = "[unblock_sub scheduler]"; sub unblock_sub(&) { my $cb = shift; @@ -655,19 +738,129 @@ } } +=item $cb = Coro::rouse_cb + +Create and return a "rouse callback". That's a code reference that, +when called, will remember a copy of its arguments and notify the owner +coro of the callback. + +See the next function. + +=item @args = Coro::rouse_wait [$cb] + +Wait for the specified rouse callback (or the last one that was created in +this coro). + +As soon as the callback is invoked (or when the callback was invoked +before C), it will return the arguments originally passed to +the rouse callback. + +See the section B for an actual usage example. + =back =cut 1; +=head1 HOW TO WAIT FOR A CALLBACK + +It is very common for a coro to wait for some callback to be +called. This occurs naturally when you use coro in an otherwise +event-based program, or when you use event-based libraries. + +These typically register a callback for some event, and call that callback +when the event occured. In a coro, however, you typically want to +just wait for the event, simplyifying things. + +For example C<< AnyEvent->child >> registers a callback to be called when +a specific child has exited: + + my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); + +But from within a coro, you often just want to write this: + + my $status = wait_for_child $pid; + +Coro offers two functions specifically designed to make this easy, +C and C. + +The first function, C, generates and returns a callback that, +when invoked, will save its arguments and notify the coro that +created the callback. + +The second function, C, waits for the callback to be called +(by calling C to go to sleep) and returns the arguments +originally passed to the callback. + +Using these functions, it becomes easy to write the C +function mentioned above: + + sub wait_for_child($) { + my ($pid) = @_; + + my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); + + my ($rpid, $rstatus) = Coro::rouse_wait; + $rstatus + } + +In the case where C and C are not flexible enough, +you can roll your own, using C: + + sub wait_for_child($) { + my ($pid) = @_; + + # store the current coro in $current, + # and provide result variables for the closure passed to ->child + my $current = $Coro::current; + my ($done, $rstatus); + + # pass a closure to ->child + my $watcher = AnyEvent->child (pid => $pid, cb => sub { + $rstatus = $_[1]; # remember rstatus + $done = 1; # mark $rstatus as valud + }); + + # wait until the closure has been called + schedule while !$done; + + $rstatus + } + + =head1 BUGS/LIMITATIONS +=over 4 + +=item fork with pthread backend + +When Coro is compiled using the pthread backend (which isn't recommended +but required on many BSDs as their libcs are completely broken), then +coro will not survive a fork. There is no known workaround except to +fix your libc and use a saner backend. + +=item perl process emulation ("threads") + This module is not perl-pseudo-thread-safe. You should only ever use this -module from the same thread (this requirement might be removed in the +module from the first thread (this requirement might be removed in the future to allow per-thread schedulers, but Coro::State does not yet allow -this). I recommend disabling thread support and using processes, as this -is much faster and uses less memory. +this). I recommend disabling thread support and using processes, as having +the windows process emulation enabled under unix roughly halves perl +performance, even when not used. + +=item coro switching is not signal safe + +You must not switch to another coro from within a signal handler +(only relevant with %SIG - most event libraries provide safe signals). + +That means you I call any function that might "block" the +current coro - C, C C<< Coro::Semaphore->down >> or +anything that calls those. Everything else, including calling C, +works. + +=back + =head1 SEE ALSO @@ -677,15 +870,18 @@ Support/Utility: L, L. -Locking/IPC: L, L, L, L, L. +Locking and IPC: L, L, L, +L, L. -IO/Timers: L, L, L, L. +I/O and Timers: L, L, L, L. -Compatibility: L, L, L, L. +Compatibility with other modules: L (but see also L for +a better-working alternative), L, L, +L. XS API: L. -Low level Configuration, Coroutine Environment: L. +Low level Configuration, Thread Environment, Continuations: L. =head1 AUTHOR