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

Comparing Coro/Coro.pm (file contents):
Revision 1.215 by root, Thu Nov 13 17:32:01 2008 UTC vs.
Revision 1.246 by root, Mon Dec 15 00:30:40 2008 UTC

 =head1 NAME
-Coro - coroutine process abstraction
+Coro - the only 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 continuations in general, most often
-multiple running interpreters that share data, which is especially useful
+in the form of cooperative threads (also called coroutines in the
-to code pseudo-parallel processes and for event-based programming, such as
+documentation). They are similar to kernel threads but don't (in general)
-multiple HTTP-GET requests running concurrently. See L<Coro::AnyEvent> to
+run in parallel at the same time even on SMP machines. The specific flavor
-learn more.
+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.
-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 threads
-they serve no purpose whatsoever, except by making your programs slow and
+very easy. And threads 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 thread is defined as "callchain + lexical variables +
-@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
+@_ + $_ + $@ + $/ + 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<Coro::State> for more configuration).
+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 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 $VERSION = 4.912;
+our $VERSION = 5.13;
 our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
 our %EXPORT_TAGS = (
       prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
 );
 our @EXPORT_OK = (@{$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
 This variable is mainly useful to integrate Coro into event loops. It is
-usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is
+usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
 pretty low-level functionality.
-This variable stores a callback that is called whenever the scheduler
+This variable stores either a coroutine or a callback.
+If it is a callback, the it is called whenever the scheduler finds no
-finds no ready coroutines to run. The default implementation prints
+ready coroutines to run. The default implementation prints "FATAL:
-"FATAL: deadlock detected" and exits, because the program has no other way
+deadlock detected" and exits, because the program has no other way to
-to continue.
+continue.
+If it is a coroutine object, then this object will be readied (without
+invoking any ready hooks, however) when the scheduler finds no other ready
+coroutines to run.
-This hook is overwritten by modules such as C<Coro::Timer> and
+This hook is overwritten by modules such as C<Coro::EV> and
 C<Coro::AnyEvent> to wait on an external event that hopefully wake up a
 coroutine so the scheduler can run it.
 Note that the callback I<must not>, 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.
+readying that coroutine in the idle handler, or by simply placing the idle
+coroutine in this variable.
 See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this
 technique.
 Please note that if your callback recursively invokes perl (e.g. for event
 $idle = sub {
    require Carp;
    Carp::croak ("FATAL: deadlock detected");
 };
-sub _cancel {
-   my ($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->prio (PRIO_MAX);
 =back
-=head2 SIMPLE COROUTINE CREATION
+=head1 SIMPLE COROUTINE CREATION
 =over 4
 =item async { ... } [@args...]
-Create a new coroutine and return it's coroutine object (usually
+Create a new coroutine and return its coroutine object (usually
 unused). The coroutine 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
 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 completly 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,
 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
 Terminates the current coroutine with the given status values (see L<cancel>).
 =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
+one. This can be useful after a fork, either in the child or the parent,
-usually only one of them should inherit the running coroutines.
+as usually only one of them should inherit the running coroutines.
+Note that in the implementation, destructors run as normal, making this
+function not so useful after a fork. Future versions of this function
+might try to free resources without running any code.
 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.
 =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 _coro_run {
    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<$throw> is specified and defined, it will be thrown as an exception
-inside the coroutine at the next convenient point in time (usually after
+inside the coroutine at the next convenient point in time. Otherwise
-it gains control at the next schedule/transfer/cede). Otherwise clears the
-exception object.
+clears the exception object.
+Coro will check for the exception each time a schedule-like-function
+returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
+>>, C<< Coro::Handle->readable >> and so on. Most of these functions
+detect this case and return early in case an exception is pending.
 The exception object will be thrown "as is" with the specified scalar in
 C<$@>, i.e. if it is a string, no line number or newline will be appended
 (unlike with C<die>).
    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
 would cause a deadlock unless there is an idle handler that wakes up some
 coroutines.
 =item my $guard = Coro::guard { ... }
-This creates and returns a guard object. Nothing happens until the object
+This function still exists, but is deprecated. Please use the
-gets destroyed, in which case the codeblock given as argument will be
+C<Guard::guard> function instead.
-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
-   }
 =cut
-sub guard(&) {
+BEGIN { *guard = \&Guard::guard }
-   bless \(my $cb = $_[0]), "Coro::guard"
-}
-sub Coro::guard::cancel {
-   ${$_[0]} = sub { };
-}
-sub Coro::guard::DESTROY {
-   ${$_[0]}->();
-}
 =item unblock_sub { ... }
 This utility function takes a BLOCK or code reference and "unblocks" it,
 returning a new coderef. Unblocking means that calling the new coderef
 original code ref will be called (with parameters) from within another
 coroutine.
 The reason this function 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,
+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<unblock_sub> is L<EV>.
 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
 # 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
    }
 };
 $unblock_scheduler->{desc} = "[unblock_sub scheduler]";
       unshift @unblock_queue, [$cb, @_];
       $unblock_scheduler->ready;
    }
 }
+=item $cb = Coro::rouse_cb
+Create and return a "rouse callback". That's a code reference that,
+when called, will remember a copy of its arguments and notify the owner
+coroutine of the callback.
+See the next function.
+=item @args = Coro::rouse_wait [$cb]
+Wait for the specified rouse callback (or the last one that was created in
+this coroutine).
+As soon as the callback is invoked (or when the callback was invoked
+before C<rouse_wait>), it will return 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 $pid;
+Coro offers two functions specifically designed to make this easy,
+C<Coro::rouse_cb> and C<Coro::rouse_wait>.
+The first function, C<rouse_cb>, generates and returns a callback that,
+when invoked, will save its arguments and notify the coroutine that
+created the callback.
+The second function, C<rouse_wait>, waits for the callback to be called
+(by calling C<schedule> to go to sleep) and returns the arguments
+originally passed to the callback.
+Using these functions, it becomes easy to write the C<wait_for_child>
+function mentioned above:
+   sub wait_for_child($) {
+      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
+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
+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 and 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>.
+I/O and 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 with other modules: 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>.
+Low level Configuration, Thread Environment, Continuations: L<Coro::State>.
 =head1 AUTHOR
  Marc Lehmann <schmorp@schmorp.de>
  http://home.schmorp.de/

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Comparing Coro/Coro.pm (file contents): Revision 1.215 by root, Thu Nov 13 17:32:01 2008 UTC vs. Revision 1.246 by root, Mon Dec 15 00:30:40 2008 UTC

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Comparing Coro/Coro.pm (file contents):
Revision 1.215 by root, Thu Nov 13 17:32:01 2008 UTC vs.
Revision 1.246 by root, Mon Dec 15 00:30:40 2008 UTC