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

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC vs.
Revision 1.297 by root, Thu May 12 23:55:39 2011 UTC

…		…
90	} 1, 2, 3;	90	} 1, 2, 3;
91		91
92	This creates a new coro thread and puts it into the ready queue, meaning	92	This creates a new coro thread and puts it into the ready queue, meaning
93	it will run as soon as the CPU is free for it.	93	it will run as soon as the CPU is free for it.
94		94
95	C<async> will return a coro object - you can store this for future	95	C<async> will return a Coro object - you can store this for future
96	reference or ignore it, the thread itself will keep a reference to it's	96	reference or ignore it - a thread that is running, ready to run or waiting
97	thread object - threads are alive on their own.	97	for some event is alive on it's own.
98		98
99	Another way to create a thread is to call the C<new> constructor with a	99	Another way to create a thread is to call the C<new> constructor with a
100	code-reference:	100	code-reference:
101		101
102	new Coro sub {	102	new Coro sub {
…		…
131	A lot can happen after the coro thread has started running. Quite usually,	131	A lot can happen after the coro thread has started running. Quite usually,
132	it will not run to the end in one go (because you could use a function	132	it will not run to the end in one go (because you could use a function
133	instead), but it will give up the CPU regularly because it waits for	133	instead), but it will give up the CPU regularly because it waits for
134	external events.	134	external events.
135		135
136	As long as a coro thread runs, it's coro object is available in the global	136	As long as a coro thread runs, its Coro object is available in the global
137	variable C<$Coro::current>.	137	variable C<$Coro::current>.
138		138
139	The low-level way to give up the CPU is to call the scheduler, which	139	The low-level way to give up the CPU is to call the scheduler, which
140	selects a new coro thread to run:	140	selects a new coro thread to run:
141		141
…		…
196		196
197	async {	197	async {
198	Coro::terminate "return value 1", "return value 2";	198	Coro::terminate "return value 1", "return value 2";
199	};	199	};
200		200
201	And yet another way is to C<< ->cancel >> the coro thread from another	201	And yet another way is to C<< ->cancel >> (or C<< ->safe_cancel >>) the
202	thread:	202	coro thread from another thread:
203		203
204	my $coro = async {	204	my $coro = async {
205	exit 1;	205	exit 1;
206	};	206	};
207		207
208	$coro->cancel; # an also accept values for ->join to retrieve	208	$coro->cancel; # also accepts values for ->join to retrieve
209		209
210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without	210	Cancellation I<can> be dangerous - it's a bit like calling C<exit> without
211	actually exiting, and might leave C libraries and XS modules in a weird	211	actually exiting, and might leave C libraries and XS modules in a weird
212	state. Unlike other thread implementations, however, Coro is exceptionally	212	state. Unlike other thread implementations, however, Coro is exceptionally
213	safe with regards to cancellation, as perl will always be in a consistent	213	safe with regards to cancellation, as perl will always be in a consistent
214	state.	214	state, and for those cases where you want to do truly marvellous things
		215	with your coro while it is being cancelled - that is, make sure all
		216	cleanup code is executed from the thread being cancelled - there is even a
		217	C<< ->safe_cancel >> method.
215		218
216	So, cancelling a thread that runs in an XS event loop might not be the	219	So, cancelling a thread that runs in an XS event loop might not be the
217	best idea, but any other combination that deals with perl only (cancelling	220	best idea, but any other combination that deals with perl only (cancelling
218	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is	221	when a thread is in a C<tie> method or an C<AUTOLOAD> for example) is
219	safe.	222	safe.
220		223
		224	Lastly, a coro thread object that isn't referenced is C<< ->cancel >>'ed
		225	automatically - just like other objects in Perl. This is not such a common
		226	case, however - a running thread is referencedy b C<$Coro::current>, a
		227	thread ready to run is referenced by the ready queue, a thread waiting
		228	on a lock or semaphore is referenced by being in some wait list and so
		229	on. But a thread that isn't in any of those queues gets cancelled:
		230
		231	async {
		232	schedule; # cede to other coros, don't go into the ready queue
		233	};
		234
		235	cede;
		236	# now the async above is destroyed, as it is not referenced by anything.
		237
221	=item 5. Cleanup	238	=item 5. Cleanup
222		239
223	Threads will allocate various resources. Most but not all will be returned	240	Threads will allocate various resources. Most but not all will be returned
224	when a thread terminates, during clean-up.	241	when a thread terminates, during clean-up.
225		242
…		…
248	# if we reutrn, or die or get cancelled, here,	265	# if we reutrn, or die or get cancelled, here,
249	# then the semaphore will be "up"ed.	266	# then the semaphore will be "up"ed.
250	};	267	};
251		268
252	The C<Guard::guard> function comes in handy for any custom cleanup you	269	The C<Guard::guard> function comes in handy for any custom cleanup you
253	might want to do:	270	might want to do (but you cannot switch to other coroutines form those
		271	code blocks):
254		272
255	async {	273	async {
256	my $window = new Gtk2::Window "toplevel";	274	my $window = new Gtk2::Window "toplevel";
257	# The window will not be cleaned up automatically, even when $window	275	# The window will not be cleaned up automatically, even when $window
258	# gets freed, so use a guard to ensure it's destruction	276	# gets freed, so use a guard to ensure it's destruction
…		…
271	# if we return or die here, the description will be restored	289	# if we return or die here, the description will be restored
272	}	290	}
273		291
274	=item 6. Viva La Zombie Muerte	292	=item 6. Viva La Zombie Muerte
275		293
276	Even after a thread has terminated and cleaned up it's resources, the coro	294	Even after a thread has terminated and cleaned up its resources, the Coro
277	object still is there and stores the return values of the thread. Only in	295	object still is there and stores the return values of the thread.
278	this state will the coro object be "reference counted" in the normal perl
279	sense: the thread code keeps a reference to it when it is active, but not
280	after it has terminated.
281		296
282	The means the coro object gets freed automatically when the thread has	297	The means the Coro object gets freed automatically when the thread has
283	terminated and cleaned up and there arenot other references.	298	terminated and cleaned up and there arenot other references.
284		299
285	If there are, the coro object will stay around, and you can call C<<	300	If there are, the Coro object will stay around, and you can call C<<
286	->join >> as many times as you wish to retrieve the result values:	301	->join >> as many times as you wish to retrieve the result values:
287		302
288	async {	303	async {
289	print "hi\n";	304	print "hi\n";
290	1	305	1
…		…
710	To avoid this, it is best to put a suspended coro into the ready queue	725	To avoid this, it is best to put a suspended coro into the ready queue
711	unconditionally, as every synchronisation mechanism must protect itself	726	unconditionally, as every synchronisation mechanism must protect itself
712	against spurious wakeups, and the one in the Coro family certainly do	727	against spurious wakeups, and the one in the Coro family certainly do
713	that.	728	that.
714		729
		730	=item $state->is_new
		731
		732	Returns true iff this Coro object is "new", i.e. has never been run
		733	yet. Those states basically consist of only the code reference to call and
		734	the arguments, but consumes very little other resources. New states will
		735	automatically get assigned a perl interpreter when they are transfered to.
		736
		737	=item $state->is_zombie
		738
		739	Returns true iff the Coro object has been cancelled, i.e.
		740	it's resources freed because they were C<cancel>'ed, C<terminate>'d,
		741	C<safe_cancel>'ed or simply went out of scope.
		742
		743	The name "zombie" stems from UNIX culture, where a process that has
		744	exited and only stores and exit status and no other resources is called a
		745	"zombie".
		746
715	=item $is_ready = $coro->is_ready	747	=item $is_ready = $coro->is_ready
716		748
717	Returns true iff the Coro object is in the ready queue. Unless the Coro	749	Returns true iff the Coro object is in the ready queue. Unless the Coro
718	object gets destroyed, it will eventually be scheduled by the scheduler.	750	object gets destroyed, it will eventually be scheduled by the scheduler.
719		751
…		…
728	Returns true iff this Coro object has been suspended. Suspended Coros will	760	Returns true iff this Coro object has been suspended. Suspended Coros will
729	not ever be scheduled.	761	not ever be scheduled.
730		762
731	=item $coro->cancel (arg...)	763	=item $coro->cancel (arg...)
732		764
733	Terminates the given Coro object and makes it return the given arguments as	765	Terminates the given Coro thread and makes it return the given arguments as
734	status (default: an empty list). Never returns if the Coro is the	766	status (default: an empty list). Never returns if the Coro is the
735	current Coro.	767	current Coro.
736		768
737	The arguments are not copied, but instead will be referenced directly	769	This is a rather brutal way to free a coro, with some limitations - if
738	(e.g. if you pass C<$var> and after the call change that variable, then	770	the thread is inside a C callback that doesn't expect to be canceled,
739	you might change the return values passed to e.g. C<join>, so don't do	771	bad things can happen, or if the cancelled thread insists on running
740	that).	772	complicated cleanup handlers that rely on it'S thread context, things will
		773	not work.
		774
		775	Any cleanup code being run (e.g. from C<guard> blocks) will be run without
		776	a thread context, and is not allowed to switch to other threads. On the
		777	plus side, C<< ->cancel >> will always clean up the thread, no matter
		778	what. If your cleanup code is complex or you want to avoid cancelling a
		779	C-thread that doesn't know how to clean up itself, it can be better to C<<
		780	->throw >> an exception, or use C<< ->safe_cancel >>.
		781
		782	The arguments to C<< ->cancel >> are not copied, but instead will
		783	be referenced directly (e.g. if you pass C<$var> and after the call
		784	change that variable, then you might change the return values passed to
		785	e.g. C<join>, so don't do that).
741		786
742	The resources of the Coro are usually freed (or destructed) before this	787	The resources of the Coro are usually freed (or destructed) before this
743	call returns, but this can be delayed for an indefinite amount of time, as	788	call returns, but this can be delayed for an indefinite amount of time, as
744	in some cases the manager thread has to run first to actually destruct the	789	in some cases the manager thread has to run first to actually destruct the
745	Coro object.	790	Coro object.
746		791
		792	=item $coro->safe_cancel ($arg...)
		793
		794	Works mostly like C<< ->cancel >>, but is inherently "safer", and
		795	consequently, can fail with an exception in cases the thread is not in a
		796	cancellable state.
		797
		798	This method works a bit like throwing an exception that cannot be caught
		799	- specifically, it will clean up the thread from within itself, so
		800	all cleanup handlers (e.g. C<guard> blocks) are run with full thread
		801	context and can block if they wish. The downside is that there is no
		802	guarantee that the thread can be cancelled when you call this method, and
		803	therefore, it might fail. It is also considerably slower than C<cancel> or
		804	C<terminate>.
		805
		806	A thread is in a safe-cancellable state if it either hasn't been run yet,
		807	or it has no C context attached and is inside an SLF function.
		808
		809	The latter two basically mean that the thread isn't currently inside a
		810	perl callback called from some C function (usually via some XS modules)
		811	and isn't currently executing inside some C function itself (via Coro's XS
		812	API).
		813
		814	This call returns true when it could cancel the thread, or croaks with an
		815	error otherwise (i.e. it either returns true or doesn't return at all).
		816
		817	Why the weird interface? Well, there are two common models on how and
		818	when to cancel things. In the first, you have the expectation that your
		819	coro thread can be cancelled when you want to cancel it - if the thread
		820	isn't cancellable, this would be a bug somewhere, so C<< ->safe_cancel >>
		821	croaks to notify of the bug.
		822
		823	In the second model you sometimes want to ask nicely to cancel a thread,
		824	but if it's not a good time, well, then don't cancel. This can be done
		825	relatively easy like this:
		826
		827	if (! eval { $coro->safe_cancel }) {
		828	warn "unable to cancel thread: $@";
		829	}
		830
		831	However, what you never should do is first try to cancel "safely" and
		832	if that fails, cancel the "hard" way with C<< ->cancel >>. That makes
		833	no sense: either you rely on being able to execute cleanup code in your
		834	thread context, or you don't. If you do, then C<< ->safe_cancel >> is the
		835	only way, and if you don't, then C<< ->cancel >> is always faster and more
		836	direct.
		837
747	=item $coro->schedule_to	838	=item $coro->schedule_to
748		839
749	Puts the current coro to sleep (like C<Coro::schedule>), but instead	840	Puts the current coro to sleep (like C<Coro::schedule>), but instead
750	of continuing with the next coro from the ready queue, always switch to	841	of continuing with the next coro from the ready queue, always switch to
751	the given coro object (regardless of priority etc.). The readyness	842	the given coro object (regardless of priority etc.). The readyness
…		…
769	inside the coro at the next convenient point in time. Otherwise	860	inside the coro at the next convenient point in time. Otherwise
770	clears the exception object.	861	clears the exception object.
771		862
772	Coro will check for the exception each time a schedule-like-function	863	Coro will check for the exception each time a schedule-like-function
773	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down	864	returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down
774	>>, C<< Coro::Handle->readable >> and so on. Most of these functions	865	>>, C<< Coro::Handle->readable >> and so on. Most of those functions (all
775	detect this case and return early in case an exception is pending.	866	that are part of Coro itself) detect this case and return early in case an
		867	exception is pending.
776		868
777	The exception object will be thrown "as is" with the specified scalar in	869	The exception object will be thrown "as is" with the specified scalar in
778	C<$@>, i.e. if it is a string, no line number or newline will be appended	870	C<$@>, i.e. if it is a string, no line number or newline will be appended
779	(unlike with C<die>).	871	(unlike with C<die>).
780		872
781	This can be used as a softer means than C<cancel> to ask a coro to	873	This can be used as a softer means than either C<cancel> or C<safe_cancel
782	end itself, although there is no guarantee that the exception will lead to	874	>to ask a coro to end itself, although there is no guarantee that the
783	termination, and if the exception isn't caught it might well end the whole	875	exception will lead to termination, and if the exception isn't caught it
784	program.	876	might well end the whole program.
785		877
786	You might also think of C<throw> as being the moral equivalent of	878	You might also think of C<throw> as being the moral equivalent of
787	C<kill>ing a coro with a signal (in this case, a scalar).	879	C<kill>ing a coro with a signal (in this case, a scalar).
788		880
789	=item $coro->join	881	=item $coro->join
790		882
791	Wait until the coro terminates and return any values given to the	883	Wait until the coro terminates and return any values given to the
792	C<terminate> or C<cancel> functions. C<join> can be called concurrently	884	C<terminate> or C<cancel> functions. C<join> can be called concurrently
793	from multiple coro, and all will be resumed and given the status	885	from multiple threads, and all will be resumed and given the status
794	return once the C<$coro> terminates.	886	return once the C<$coro> terminates.
795		887
796	=cut
797
798	sub join {
799	my $self = shift;
800
801	unless ($self->{_status}) {
802	my $current = $current;
803
804	push @{$self->{_on_destroy}}, sub {
805	$current->ready;
806	undef $current;
807	};
808
809	&schedule while $current;
810	}
811
812	wantarray ? @{$self->{_status}} : $self->{_status}[0];
813	}
814
815	=item $coro->on_destroy (\&cb)	888	=item $coro->on_destroy (\&cb)
816		889
817	Registers a callback that is called when this coro thread gets destroyed,	890	Registers a callback that is called when this coro thread gets destroyed,
818	but before it is joined. The callback gets passed the terminate arguments,	891	that is, after it's resources have been freed but before it is joined. The
		892	callback gets passed the terminate/cancel arguments, if any, and I<must
819	if any, and I<must not> die, under any circumstances.	893	not> die, under any circumstances.
820		894
821	There can be any number of C<on_destroy> callbacks per coro.	895	There can be any number of C<on_destroy> callbacks per coro, and there is
822		896	no way currently to remove a callback once added.
823	=cut
824
825	sub on_destroy {
826	my ($self, $cb) = @_;
827
828	push @{ $self->{_on_destroy} }, $cb;
829	}
830		897
831	=item $oldprio = $coro->prio ($newprio)	898	=item $oldprio = $coro->prio ($newprio)
832		899
833	Sets (or gets, if the argument is missing) the priority of the	900	Sets (or gets, if the argument is missing) the priority of the
834	coro thread. Higher priority coro get run before lower priority	901	coro thread. Higher priority coro get run before lower priority
…		…
1106	future to allow per-thread schedulers, but Coro::State does not yet allow	1173	future to allow per-thread schedulers, but Coro::State does not yet allow
1107	this). I recommend disabling thread support and using processes, as having	1174	this). I recommend disabling thread support and using processes, as having
1108	the windows process emulation enabled under unix roughly halves perl	1175	the windows process emulation enabled under unix roughly halves perl
1109	performance, even when not used.	1176	performance, even when not used.
1110		1177
		1178	Attempts to use threads created in another emulated process will crash
		1179	("cleanly", with a null pointer exception).
		1180
1111	=item coro switching is not signal safe	1181	=item coro switching is not signal safe
1112		1182
1113	You must not switch to another coro from within a signal handler (only	1183	You must not switch to another coro from within a signal handler (only
1114	relevant with %SIG - most event libraries provide safe signals), I<unless>	1184	relevant with %SIG - most event libraries provide safe signals), I<unless>
1115	you are sure you are not interrupting a Coro function.	1185	you are sure you are not interrupting a Coro function.

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Comparing cvsroot/Coro/Coro.pm (file contents): Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC vs. Revision 1.297 by root, Thu May 12 23:55:39 2011 UTC

Diff Legend

Comparing cvsroot/Coro/Coro.pm (file contents):
Revision 1.291 by root, Fri Apr 29 15:43:26 2011 UTC vs.
Revision 1.297 by root, Thu May 12 23:55:39 2011 UTC