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

Comparing Coro/Coro.pm (file contents):
Revision 1.246 by root, Mon Dec 15 00:30:40 2008 UTC vs.
Revision 1.266 by root, Wed Aug 26 07:41:07 2009 UTC

      print "2\n";
      cede; # yield back to main
      print "4\n";
   };
   print "1\n";
-  cede; # yield to coroutine
+  cede; # yield to coro
   print "3\n";
   cede; # and again
   # use locking
   use Coro::Semaphore;
 =head1 DESCRIPTION
 For a tutorial-style introduction, please read the L<Coro::Intro>
 manpage. This manpage mainly contains reference information.
-This module collection manages continuations in general, most often
+This module collection manages continuations in general, most often in
-in the form of cooperative threads (also called coroutines in the
+the form of cooperative threads (also called coros, or simply "coro"
-documentation). They are similar to kernel threads but don't (in general)
+in the documentation). They are similar to kernel threads but don't (in
-run in parallel at the same time even on SMP machines. The specific flavor
+general) run in parallel at the same time even on SMP machines. The
-of thread offered by this module also guarantees you that it will not
+specific flavor of thread offered by this module also guarantees you that
-switch between threads unless necessary, at easily-identified points in
+it will not switch between threads unless necessary, at easily-identified
-your program, so locking and parallel access are rarely an issue, making
+points in your program, so locking and parallel access are rarely an
-thread programming much safer and easier than using other thread models.
+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), Coro provides a
+but only the windows process emulation (see section of same name for more
+details) ported to unix, and as such act as processes), Coro provides
-full shared address space, which makes communication between threads
+a full shared address space, which makes communication between threads
-very easy. And threads are fast, too: disabling the Windows process
+very easy. And Coro's threads are fast, too: disabling the Windows
-emulation code in your perl and using Coro can easily result in a two to
+process emulation code in your perl and using Coro can easily result in
-four times speed increase for your programs.
+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<Coro::AnyEvent> to learn more on how to integrate Coro
 into an event-based environment.
 In this module, a thread is defined as "callchain + lexical variables +
-@_ + $_ + $@ + $/ + C stack), that is, a thread has its own callchain,
+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<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.
 use Coro::State;
 use base qw(Coro::State Exporter);
 our $idle;    # idle handler
-our $main;    # main coroutine
+our $main;    # main coro
-our $current; # current coroutine
+our $current; # current coro
-our $VERSION = 5.13;
+our $VERSION = 5.17;
 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)],
 );
 =over 4
 =item $Coro::main
-This variable stores the coroutine object that represents the main
+This variable stores the Coro object that represents the main
 program. While you cna C<ready> it and do most other things you can do to
-coroutines, it is mainly useful to compare again C<$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 is now being initialised by Coro::State
 =item $Coro::current
-The coroutine object representing the current coroutine (the last
+The Coro object representing the current coro (the last
-coroutine that the Coro scheduler switched to). The initial value is
+coro that the Coro scheduler switched to). The initial value is
 C<$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
+value stored in it and use it as any other Coro object, but you must
 not otherwise modify the variable itself.
 =cut
 sub current() { $current } # [DEPRECATED]
 This variable is mainly useful to integrate Coro into event loops. It is
 usually better to rely on L<Coro::AnyEvent> or L<Coro::EV>, as this is
 pretty low-level functionality.
-This variable stores either a coroutine or a callback.
+This variable stores either a Coro object or a callback.
 If it is a callback, the it is called whenever the scheduler finds no
-ready coroutines to run. The default implementation prints "FATAL:
+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 coroutine object, then this object will be readied (without
+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
-coroutines to run.
+coros to run.
 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.
+coro 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
+the current coro. Normally, this is achieved by having an "idle
-coroutine" that calls the event loop and then blocks again, and then
+coro" that calls the event loop and then blocks again, and then
-readying that coroutine in the idle handler, or by simply placing the idle
+readying that coro in the idle handler, or by simply placing the idle
-coroutine in this variable.
+coro 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");
 };
-# this coroutine is necessary because a coroutine
+# this coro is necessary because a coro
 # cannot destroy itself.
 our @destroy;
 our $manager;
 $manager = new Coro sub {
    while () {
-      Coro::_cancel shift @destroy
+      Coro::State::cancel shift @destroy
          while @destroy;
       &schedule;
    }
 };
 $manager->{desc} = "[coro manager]";
 $manager->prio (PRIO_MAX);
 =back
-=head1 SIMPLE COROUTINE CREATION
+=head1 SIMPLE CORO CREATION
 =over 4
 =item async { ... } [@args...]
-Create a new coroutine and return its coroutine object (usually
+Create a new coro and return its Coro object (usually
-unused). The coroutine will be put into the ready queue, so
+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<Coro::State::new> constructor for info about the coroutine
+See the C<Coro::State::new> constructor for info about the coro
-environment in which coroutines are executed.
+environment in which coro are executed.
-Calling C<exit> in a coroutine will do the same as calling exit outside
+Calling C<exit> in a coro will do the same as calling exit outside
-the coroutine. Likewise, when the coroutine dies, the program will exit,
+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<die> handler, or
 simply avoid dieing (by use of C<eval>).
-Example: Create a new coroutine that just prints its arguments.
+Example: Create a new coro that just prints its arguments.
    async {
       print "@_\n";
    } 1,2,3,4;
-=cut
-sub async(&@) {
-   my $coro = new Coro @_;
-   $coro->ready;
-   $coro
-}
 =item async_pool { ... } [@args...]
-Similar to C<async>, but uses a coroutine pool, so you should not call
+Similar to C<async>, but uses a coro pool, so you should not call
 terminate or join on it (although you are allowed to), and you get a
-coroutine that might have executed other code already (which can be good
+coro that might have executed other code already (which can be good
 or bad :).
 On the plus side, this function is about twice as fast as creating (and
-destroying) a completely new coroutine, so if you need a lot of generic
+destroying) a completely new coro, so if you need a lot of generic
-coroutines in quick successsion, use C<async_pool>, not C<async>.
+coros in quick successsion, use C<async_pool>, not C<async>.
 The code block is executed in an C<eval> context and a warning will be
 issued in case of an exception instead of terminating the program, as
-C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
+C<async> does. As the coro is being reused, stuff like C<on_destroy>
 will not work in the expected way, unless you call terminate or cancel,
 which somehow defeats the purpose of pooling (but is fine in the
 exceptional case).
 The priority will be reset to C<0> after each run, tracing will be
 disabled, the description will be reset and the default output filehandle
-gets restored, so you can change all these. Otherwise the coroutine will
+gets restored, so you can change all these. Otherwise the coro will
-be re-used "as-is": most notably if you change other per-coroutine global
+be re-used "as-is": most notably if you change other per-coro global
 stuff such as C<$/> you I<must needs> 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<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 32kb
 (adjustable via $Coro::POOL_RSS) it will also be destroyed.
 =back
 =head1 STATIC METHODS
 Static methods are actually functions that implicitly operate on the
-current coroutine.
+current coro.
 =over 4
 =item schedule
-Calls the scheduler. The scheduler will find the next coroutine that is
+Calls the scheduler. The scheduler will find the next coro that is
-to be run from the ready queue and switches to it. The next coroutine
+to be run from the ready queue and switches to it. The next coro
 to be run is simply the one with the highest priority that is longest
-in its ready queue. If there is no coroutine ready, it will clal the
+in its ready queue. If there is no coro ready, it will clal the
 C<$Coro::idle> hook.
-Please note that the current coroutine will I<not> be put into the ready
+Please note that the current coro will I<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 C<< ->ready >>,
 thus waking you up.
 This makes C<schedule> I<the> 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<schedule> 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.
 See B<HOW TO WAIT FOR A CALLBACK>, 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<schedule>, which has the effect of giving
-up the current "timeslice" to other coroutines of the same or higher
+up the current "timeslice" to other coros of the same or higher
-priority. Once your coroutine gets its turn again it will automatically be
+priority. Once your coro gets its turn again it will automatically be
 resumed.
 This function is often called C<yield> in other languages.
 =item Coro::cede_notself
 Works like cede, but is not exported by default and will cede to I<any>
-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<cancel>).
+Terminates the current coro with the given status values (see L<cancel>).
+=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<Neither invoking the scheduler, nor exceptions, are allowed within those
+BLOCKs>. That means: do not even think about calling C<die> 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<dynamic-wind> 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<tzset>, but by using C<on_enter> and C<on_leave>,
+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
+Kills/terminates/cancels all coros except the currently running one.
-one. This can be useful after a fork, either in the child or the parent,
-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,
+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
-you cannot free all of them, so if a coroutine that is not the main
+cannot free all of them, so if a coro that is not the main coro
-program calls this function, there will be some one-time resource leak.
+calls this function, there will be some one-time resource leak.
 =cut
 sub killall {
    for (Coro::State::list) {
    }
 }
 =back
-=head1 COROUTINE OBJECT 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<terminate> 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<async> and C<Coro::State::new> for additional info about the
-coroutine environment.
+coro environment.
 =cut
 sub _coro_run {
    terminate &{+shift};
 }
-=item $success = $coroutine->ready
+=item $success = $coro->ready
-Put the given coroutine into the end of its ready queue (there is one
+Put the given coro into the end of its ready queue (there is one
-queue for each priority) and return true. If the coroutine is already in
+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
+This ensures that the scheduler will resume this coro automatically
-once all the coroutines of higher priority and all coroutines of the same
+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 $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 = $coroutine->is_ready
+=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 $is_running = $coro->is_running
+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 $coroutine->cancel (arg...)
+=item $coro->cancel (arg...)
-Terminates the given coroutine and makes it return the given arguments as
+Terminates the given Coro and makes it return the given arguments as
-status (default: the empty list). Never returns if the coroutine is the
+status (default: the empty list). Never returns if the Coro is the
-current coroutine.
+current Coro.
 =cut
 sub cancel {
    my $self = shift;
    if ($current == $self) {
       terminate @_;
    } else {
       $self->{_status} = [@_];
-      $self->_cancel;
+      Coro::State::cancel $self;
    }
 }
-=item $coroutine->schedule_to
+=item $coro->schedule_to
-Puts the current coroutine to sleep (like C<Coro::schedule>), but instead
+Puts the current coro 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
+the given coro object (regardless of priority etc.). The readyness
-state of that coroutine isn't changed.
+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 $coroutine->cede_to
+=item $coro->cede_to
-Like C<schedule_to>, but puts the current coroutine into the ready
+Like C<schedule_to>, but puts the current coro into the ready
 queue. This has the effect of temporarily switching to the given
-coroutine, and continuing some time later.
+coro, 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])
+=item $coro->throw ([$scalar])
 If C<$throw> is specified and defined, it will be thrown as an exception
-inside the coroutine at the next convenient point in time. Otherwise
+inside the coro at the next convenient point in time. Otherwise
 clears the exception object.
 Coro will check for the exception each time a schedule-like-function
 returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
 >>, C<< Coro::Handle->readable >> and so on. Most of these functions
 The exception object will be thrown "as is" with the specified scalar in
 C<$@>, 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
+This can be used as a softer means than C<cancel> 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<throw> as being the moral equivalent of
-C<kill>ing a coroutine with a signal (in this case, a scalar).
+C<kill>ing a coro with a signal (in this case, a scalar).
-=item $coroutine->join
+=item $coro->join
-Wait until the coroutine terminates and return any values given to the
+Wait until the coro terminates and return any values given to the
 C<terminate> or C<cancel> functions. C<join> can be called concurrently
-from multiple coroutines, and all will be resumed and given the status
+from multiple coro, and all will be resumed and given the status
-return once the C<$coroutine> terminates.
+return once the C<$coro> terminates.
 =cut
 sub join {
    my $self = shift;
    }
    wantarray ? @{$self->{_status}} : $self->{_status}[0];
 }
-=item $coroutine->on_destroy (\&cb)
+=item $coro->on_destroy (\&cb)
-Registers a callback that is called when this coroutine gets destroyed,
+Registers a callback that is called when this coro gets destroyed,
 but before it is joined. The callback gets passed the terminate arguments,
 if any, and I<must not> die, under any circumstances.
 =cut
    my ($self, $cb) = @_;
    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
+coro. Higher priority coro get run before lower priority
-coroutines. Priorities are small signed integers (currently -4 .. +3),
+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):
    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);
+   current->prio (PRIO_HIGH);
-The idle coroutine ($Coro::idle) always has a lower priority than any
+The idle coro ($Coro::idle) always has a lower priority than any
-existing coroutine.
+existing coro.
-Changing the priority of the current coroutine will take effect immediately,
+Changing the priority of the current coro will take effect immediately,
-but changing the priority of coroutines in the ready queue (but not
+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<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)
+=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
+coro. This is just a free-form string you can associate with a
-coroutine.
+coro.
-This method simply sets the C<< $coroutine->{desc} >> member to the given
+This method simply sets the C<< $coro->{desc} >> member to the given
 string. You can modify this member directly if you wish.
 =cut
 sub desc {
 =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<schedule> 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<cede> would have no effect, and C<schedule>
 would cause a deadlock unless there is an idle handler that wakes up some
-coroutines.
+coro.
 =item my $guard = Coro::guard { ... }
 This function still exists, but is deprecated. Please use the
 C<Guard::guard> function instead.
 This utility function takes a BLOCK or code reference and "unblocks" it,
 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<Event|Event> module) are not coroutine-safe (a weaker form
+venerable L<Event|Event> 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<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
+coro 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, for example.
 In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
 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),
+another coro, or puts some other coro into the ready queue), there is
-there is no reason to use C<unblock_sub>.
+no reason to use C<unblock_sub>.
 Note that you also need to use C<unblock_sub> for any other callbacks that
 are indirectly executed by any C-based event loop. For example, when you
 use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it
 provides callbacks that are the result of some event callback, then you
 =item $cb = Coro::rouse_cb
 Create and return a "rouse callback". That's a code reference that,
 when called, will remember a copy of its arguments and notify the owner
-coroutine of the callback.
+coro of the callback.
 See the next function.
 =item @args = Coro::rouse_wait [$cb]
 Wait for the specified rouse callback (or the last one that was created in
-this coroutine).
+this coro).
 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.
+the rouse callback. In scalar context, that means you get the I<last>
+argument, just as if C<rouse_wait> had a C<return ($a1, $a2, $a3...)>
+statement at the end.
 See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example.
 =back
 1;
 =head1 HOW TO WAIT FOR A CALLBACK
-It is very common for a coroutine to wait for some callback to be
+It is very common for a coro to wait for some callback to be
-called. This occurs naturally when you use coroutines in an otherwise
+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 coroutine, however, you typically want to
+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 withina coroutine, you often just want to write this:
+But from within a coro, you often just want to write this:
    my $status = wait_for_child $pid;
 Coro offers two functions specifically designed to make this easy,
 C<Coro::rouse_cb> and C<Coro::rouse_wait>.
 The first function, C<rouse_cb>, generates and returns a callback that,
-when invoked, will save its arguments and notify the coroutine that
+when invoked, will save its arguments and notify the coro that
 created the callback.
 The second function, C<rouse_wait>, waits for the callback to be called
 (by calling C<schedule> to go to sleep) and returns the arguments
 originally passed to the callback.
 you can roll your own, using C<schedule>:
    sub wait_for_child($) {
       my ($pid) = @_;
-      # store the current coroutine in $current,
+      # 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
 =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
+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
 future to allow per-thread schedulers, but Coro::State does not yet allow
 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 coroutine switching not signal safe
+=item coro switching is not signal safe
-You must not switch to another coroutine from within a signal handler
+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<MUST NOT> call any function that might "block" the
-current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
+current coro - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or
 anything that calls those. Everything else, including calling C<ready>,
 works.
 =back
+=head1 WINDOWS PROCESS EMULATION
+A great many people seem to be confused about ithreads (for example, Chip
+Salzenberg called me unintelligent, incapable, stupid and ingullible,
+while in the same mail making rather confused statements about perl
+ithreads (for example, that memory or files would be shared), showing his
+lack of understanding of this area - if it is hard to understand for Chip,
+it is probably not obvious to everybody).
+What follows is an ultra-condensed version of my talk about threads in
+scripting languages given onthe perl workshop 2009:
+The so-called "ithreads" were originally implemented for two reasons:
+first, to (badly) emulate unix processes on native win32 perls, and
+secondly, to replace the older, real thread model ("5.005-threads").
+It does that by using threads instead of OS processes. The difference
+between processes and threads is that threads share memory (and other
+state, such as files) between threads within a single process, while
+processes do not share anything (at least not semantically). That
+means that modifications done by one thread are seen by others, while
+modifications by one process are not seen by other processes.
+The "ithreads" work exactly like that: when creating a new ithreads
+process, all state is copied (memory is copied physically, files and code
+is copied logically). Afterwards, it isolates all modifications. On UNIX,
+the same behaviour can be achieved by using operating system processes,
+except that UNIX typically uses hardware built into the system to do this
+efficiently, while the windows process emulation emulates this hardware in
+software (rather efficiently, but of course it is still much slower than
+dedicated hardware).
+As mentioned before, loading code, modifying code, modifying data
+structures and so on is only visible in the ithreads process doing the
+modification, not in other ithread processes within the same OS process.
+This is why "ithreads" do not implement threads for perl at all, only
+processes. What makes it so bad is that on non-windows platforms, you can
+actually take advantage of custom hardware for this purpose (as evidenced
+by the forks module, which gives you the (i-) threads API, just much
+faster).
+Sharing data is in the i-threads model is done by transfering data
+structures between threads using copying semantics, which is very slow -
+shared data simply does not exist. Benchmarks using i-threads which are
+communication-intensive show extremely bad behaviour with i-threads (in
+fact, so bad that Coro, which cannot take direct advantage of multiple
+CPUs, is often orders of magnitude faster because it shares data using
+real threads, refer to my talk for details).
+As summary, i-threads *use* threads to implement processes, while
+the compatible forks module *uses* processes to emulate, uhm,
+processes. I-threads slow down every perl program when enabled, and
+outside of windows, serve no (or little) practical purpose, but
+disadvantages every single-threaded Perl program.
+This is the reason that I try to avoid the name "ithreads", as it is
+misleading as it implies that it implements some kind of thread model for
+perl, and prefer the name "windows process emulation", which describes the
+actual use and behaviour of it much better.
 =head1 SEE ALSO
 Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.

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Revision 1.266 by root, Wed Aug 26 07:41:07 2009 UTC