[ViewVC] Diff of: cvs/Coro/Coro.pm

Comparing Coro/Coro.pm (file contents):
Revision 1.202 by root, Tue Sep 30 17:12:34 2008 UTC vs.
Revision 1.237 by root, Sat Nov 22 16:37:11 2008 UTC

 =head1 NAME
-Coro - coroutine process abstraction
+Coro - real threads in perl
 =head1 SYNOPSIS
   use Coro;
   $locked = 1;
   $lock->up;
 =head1 DESCRIPTION
-This module collection manages coroutines. Coroutines are similar to
+For a tutorial-style introduction, please read the L<Coro::Intro>
-threads but don't (in general) run in parallel at the same time even
+manpage. This manpage mainly contains reference information.
-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
+This module collection manages coroutines, that is, cooperative
-multiple running interpreters that share data, which is especially useful
+threads. Coroutines are similar to kernel threads but don't (in general)
-to code pseudo-parallel processes and for event-based programming, such as
+run in parallel at the same time even on SMP machines. The specific flavor
-multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
+of coroutine used in this module also guarantees you that it will not
-learn more.
+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 using other thread
+models.
-Coroutines are also useful because Perl has no support for threads (the so
+Unlike the so-called "Perl threads" (which are not actually real threads
-called "threads" that perl offers are nothing more than the (bad) process
+but only the windows process emulation ported to unix), Coro provides a
-emulation coming from the Windows platform: On standard operating systems
+full shared address space, which makes communication between coroutines
-they serve no purpose whatsoever, except by making your programs slow and
+very easy. And coroutines are fast, too: disabling the Windows process
-making them use a lot of memory. Best disable them when building perl, or
+emulation code in your perl and using Coro can easily result in a two to
-aks your software vendor/distributor to do it for you).
+four times speed increase for your programs.
+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<Coro::AnyEvent> to learn more on how to integrate Coro
+into an event-based environment.
-In this module, coroutines are defined as "callchain + lexical variables +
+In this module, a coroutines is defined as "callchain + lexical variables
-@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
++ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own
-its own set of lexicals and its own set of perls most important global
+callchain, its own set of lexicals and its own set of perls most important
-variables (see L<Coro::State> for more configuration).
+global variables (see L<Coro::State> for more configuration and background
+info).
+See also the C<SEE ALSO> 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 Coro::State;
 use base qw(Coro::State Exporter);
 our $idle;    # idle handler
 our $main;    # main coroutine
 our $current; # current coroutine
-our $VERSION = 4.8;
+our $VERSION = "5.0";
 our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
 our %EXPORT_TAGS = (
       prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
 );
 our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
+=head1 GLOBAL VARIABLES
 =over 4
 =item $Coro::main
 This variable stores the coroutine object that represents the main
 coroutines, it is mainly useful to compare again C<$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).
+C<$Coro::main> (of course).
 This variable is B<strictly> I<read-only>. You can take copies of the
 value stored in it and use it as any other coroutine object, but you must
 not otherwise modify the variable itself.
 =cut
-$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
 $idle = sub {
    require Carp;
    Carp::croak ("FATAL: deadlock detected");
 };
-sub _cancel {
-   my ($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
 # cannot destroy itself.
-my @destroy;
+our @destroy;
-my $manager;
+our $manager;
 $manager = new Coro sub {
    while () {
-      (shift @destroy)->_cancel
+      Coro::_cancel shift @destroy
          while @destroy;
       &schedule;
    }
 };
-$manager->desc ("[coro manager]");
+$manager->{desc} = "[coro manager]";
 $manager->prio (PRIO_MAX);
 =back
-=head2 SIMPLE COROUTINE CREATION
+=head1 SIMPLE COROUTINE CREATION
 =over 4
 =item async { ... } [@args...]
 Similar to C<async>, but uses a coroutine pool, so you should not call
 terminate or join on it (although you are allowed to), and you get a
 coroutine that might have executed other code already (which can be good
 or bad :).
-On the plus side, this function is faster than creating (and destroying)
+On the plus side, this function is about twice as fast as creating (and
-a completely new coroutine, so if you need a lot of generic coroutines in
+destroying) a completely new coroutine, so if you need a lot of generic
-quick successsion, use C<async_pool>, not C<async>.
+coroutines in quick successsion, use C<async_pool>, not C<async>.
 The code block is executed in an C<eval> context and a warning will be
 issued in case of an exception instead of terminating the program, as
 C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
 will not work in the expected way, unless you call terminate or cancel,
 The priority will be reset to C<0> after each run, tracing will be
 disabled, the description will be reset and the default output filehandle
 gets restored, so you can change all these. Otherwise the coroutine will
 be re-used "as-is": most notably if you change other per-coroutine global
-stuff such as C<$/> you I<must needs> to revert that change, which is most
+stuff such as C<$/> you I<must needs> revert that change, which is most
-simply done by using local as in: C< local $/ >.
+simply done by using local as in: C<< local $/ >>.
-The pool size is limited to C<8> idle coroutines (this can be adjusted by
+The idle pool size is limited to C<8> idle coroutines (this can be
-changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
+adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle
-required.
+coros as required.
 If you are concerned about pooled coroutines growing a lot because a
 single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
 { terminate }> 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_handler} while 1;
-            _pool_1 $cb;
-            &$cb;
-            _pool_2 $cb;
-            &schedule;
-         }
       };
-      if ($@) {
-         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 coroutine.
 =over 4
 =item schedule
 >> on that once some event happens, and last you call C<schedule> to put
 yourself to sleep. Note that a lot of things can wake your coroutine 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:
+See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks.
-   {
-      # 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;
-   }
 =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
 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.
 =cut
-sub terminate {
-   $current->cancel (@_);
-}
 sub killall {
    for (Coro::State::list) {
       $_->cancel
          if $_ != $current && UNIVERSAL::isa $_, "Coro";
    }
 }
 =back
-=head2 COROUTINE METHODS
+=head1 COROUTINE OBJECT METHODS
 These are the methods you can call on coroutine objects (or to create
 them).
 =over 4
 See C<async> and C<Coro::State::new> for additional info about the
 coroutine environment.
 =cut
-sub _run_coro {
+sub _terminate {
    terminate &{+shift};
-}
-sub new {
-   my $class = shift;
-   $class->SUPER::new (\&_run_coro, @_)
 }
 =item $success = $coroutine->ready
 Put the given coroutine into the end of its ready queue (there is one
 =cut
 sub cancel {
    my $self = shift;
-   $self->{_status} = [@_];
    if ($current == $self) {
-      push @destroy, $self;
+      terminate @_;
-      $manager->ready;
-      &schedule while 1;
    } else {
+      $self->{_status} = [@_];
       $self->_cancel;
    }
 }
+=item $coroutine->schedule_to
+Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
+of continuing with the next coro from the ready queue, always switch to
+the given coroutine object (regardless of priority etc.). The readyness
+state of that coroutine isn't changed.
+This is an advanced method for special cases - I'd love to hear about any
+uses for this one.
+=item $coroutine->cede_to
+Like C<schedule_to>, but puts the current coroutine into the ready
+queue. This has the effect of temporarily switching to the given
+coroutine, and continuing some time later.
+This is an advanced method for special cases - I'd love to hear about any
+uses for this one.
+=item $coroutine->throw ([$scalar])
+If C<$throw> is specified and defined, it will be thrown as an exception
+inside the coroutine at the next convenient point in time. Otherwise
+clears the exception object.
+Coro will check for the exception each time a schedule-like-function
+returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
+>>, C<< Coro::Handle->readable >> and so on. Most of these functions
+detect this case and return early in case an exception is pending.
+The exception object will be thrown "as is" with the specified scalar in
+C<$@>, i.e. if it is a string, no line number or newline will be appended
+(unlike with C<die>).
+This can be used as a softer means than C<cancel> to ask a coroutine 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<throw> as being the moral equivalent of
+C<kill>ing a coroutine with a signal (in this case, a scalar).
 =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 concurrently
 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.
+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
+This method simply sets the C<< $coroutine->{desc} >> member to the given
-can modify this member directly if you wish.
+string. You can modify this member directly if you wish.
-=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<die>).
-This can be used as a softer means than C<cancel> 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.
 =cut
 sub desc {
    my $old = $_[0]{desc};
    $_[0]{desc} = $_[1] if @_ > 1;
    $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
 # return immediately and can be reused) and because we cannot cede
 # inside an event callback.
 our $unblock_scheduler = new Coro sub {
    while () {
       while (my $cb = pop @unblock_queue) {
-         # this is an inlined copy of async_pool
+         &async_pool (@$cb);
-         my $coro = (pop @async_pool) || new Coro \&pool_handler;
-         $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 $cb = shift;
    sub {
       unshift @unblock_queue, [$cb, @_];
       $unblock_scheduler->ready;
    }
 }
+=item $cb = Coro::rouse_cb
+Create and return a "rouse callback". That's a code reference that, when
+called, will save its arguments and notify the owner coroutine of the
+callback.
+See the next function.
+=item @args = Coro::rouse_wait [$cb]
+Wait for the specified rouse callback (or the last one tht was created in
+this coroutine).
+As soon as the callback is invoked (or when the calback was invoked before
+C<rouse_wait>), it will return a copy of the arguments originally passed
+to the rouse callback.
+See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
 =back
 =cut
 1;
+=head1 HOW TO WAIT FOR A CALLBACK
+It is very common for a coroutine to wait for some callback to be
+called. This occurs naturally when you use coroutines 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 coroutine, 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 withina coroutine, you often just want to write this:
+   my $status = wait_for_child $pid;
+Coro offers two functions specifically designed to make this easy,
+C<Coro::rouse_cb> and C<Coro::rouse_wait>.
+The first function, C<rouse_cb>, generates and returns a callback that,
+when invoked, will save it's arguments and notify the coroutine that
+created the callback.
+The second function, C<rouse_wait>, waits for the callback to be called
+(by calling C<schedule> to go to sleep) and returns the arguments
+originally passed to the callback.
+Using these functions, it becomes easy to write the C<wait_for_child>
+function mentioned above:
+   sub wait_for_child($) {
+      my ($pid) = @_;
+      my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb);
+      my ($rpid, $rstatus) = Coro::rouse_wait;
+      $rstatus
+   }
+In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough,
+you can roll your own, using C<schedule>:
+   sub wait_for_child($) {
+      my ($pid) = @_;
+      # store the current coroutine 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
+coroutines 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
 future to allow per-thread schedulers, but Coro::State does not yet allow
-this). I recommend disabling thread support and using processes, as this
+this). I recommend disabling thread support and using processes, as having
-is much faster and uses less memory.
+the windows process emulation enabled under unix roughly halves perl
+performance, even when not used.
+=item coroutine switching not signal safe
+You must not switch to another coroutine from within a signal handler
+(only relevant with %SIG - most event libraries provide safe signals).
+That means you I<MUST NOT> call any function that might "block" the
+current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
+anything that calls those. Everything else, including calling C<ready>,
+works.
+=back
 =head1 SEE ALSO
 Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
 Debugging: L<Coro::Debug>.
 Support/Utility: L<Coro::Specific>, L<Coro::Util>.
-Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
+Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>,
+L<Coro::SemaphoreSet>, L<Coro::RWLock>.
 IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>.
-Compatibility: L<Coro::LWP>, L<Coro::BDB>, L<Coro::Storable>, L<Coro::Select>.
+Compatibility: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for
+a better-working alternative), L<Coro::BDB>, L<Coro::Storable>,
+L<Coro::Select>.
 XS API: L<Coro::MakeMaker>.
 Low level Configuration, Coroutine Environment: L<Coro::State>.

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Comparing Coro/Coro.pm (file contents): Revision 1.202 by root, Tue Sep 30 17:12:34 2008 UTC vs. Revision 1.237 by root, Sat Nov 22 16:37:11 2008 UTC

Diff Legend

Comparing Coro/Coro.pm (file contents):
Revision 1.202 by root, Tue Sep 30 17:12:34 2008 UTC vs.
Revision 1.237 by root, Sat Nov 22 16:37:11 2008 UTC