[ViewVC] Diff of: cvs/cvsroot/Async-Interrupt/Interrupt.pm

Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents):
Revision 1.10 by root, Sun Jul 12 23:03:36 2009 UTC vs.
Revision 1.18 by root, Tue Jul 28 12:50:16 2009 UTC

…		…
53		53
54	For example the deliantra game server uses a variant of this technique	54	For example the deliantra game server uses a variant of this technique
55	to interrupt background processes regularly to send map updates to game	55	to interrupt background processes regularly to send map updates to game
56	clients.	56	clients.
57		57
		58	Or L<EV::Loop::Async> uses an interrupt object to wake up perl when new
		59	events have arrived.
		60
58	L<IO::AIO> and L<BDB> could also use this to speed up result reporting.	61	L<IO::AIO> and L<BDB> could also use this to speed up result reporting.
59		62
60	=item Speedy event loop invocation	63	=item Speedy event loop invocation
61		64
62	One could use this module e.g. in L<Coro> to interrupt a running coro-thread	65	One could use this module e.g. in L<Coro> to interrupt a running coro-thread
…		…
88	I<running> interpreter, there is optional support for signalling a pipe	91	I<running> interpreter, there is optional support for signalling a pipe
89	- that means you can also wait for the pipe to become readable (e.g. via	92	- that means you can also wait for the pipe to become readable (e.g. via
90	L<EV> or L<AnyEvent>). This, of course, incurs the overhead of a C<read>	93	L<EV> or L<AnyEvent>). This, of course, incurs the overhead of a C<read>
91	and C<write> syscall.	94	and C<write> syscall.
92		95
		96	=head1 USAGE EXAMPLES
		97
		98	=head2 Async::Interrupt to implement race-free signal handling
		99
		100	This example uses a single event pipe for all signals, and one
		101	Async::Interrupt per signal.
		102
		103	First, create the event pipe and hook it into the event loop (this code is
		104	actually what L<AnyEvent> uses itself):
		105
		106	$SIGPIPE = new Async::Interrupt::EventPipe;
		107	$SIGPIPE_W = AnyEvent->io (
		108	fh => $SIGPIPE->fileno,
		109	poll => "r",
		110	cb => \&_signal_check,
		111	);
		112
		113	Then, for each signal to hook, create an Async::Interrupt object. The
		114	callback just sets a global variable, as we are only interested in
		115	synchronous signals (i.e. when the event loop polls), which is why the
		116	pipe draining is not done automatically.
		117
		118	my $interrupt = new Async::Interrupt
		119	cb => sub { undef $SIGNAL_RECEIVED{$signum} }
		120	signal => $signal,
		121	pipe => [$SIGPIPE_R->filenos],
		122	pipe_autodrain => 0,
		123	;
		124
		125	Finally, the I/O callback for the event pipe handles the signals:
		126
		127	sub _signal_check {
		128	# drain the pipe first
		129	$SIGPIPE->drain;
		130
		131	# two loops, just to be sure
		132	while (%SIGNAL_RECEIVED) {
		133	for (keys %SIGNAL_RECEIVED) {
		134	delete $SIGNAL_RECEIVED{$_};
		135	warn "signal $_ received\n";
		136	}
		137	}
		138	}
		139
		140
		141
		142	=head1 THE Async::Interrupt CLASS
		143
93	=over 4	144	=over 4
94		145
95	=cut	146	=cut
96		147
97	package Async::Interrupt;	148	package Async::Interrupt;
98		149
99	use common::sense;	150	use common::sense;
100		151
101	BEGIN {	152	BEGIN {
		153	# the next line forces initialisation of internal
		154	# signal handling # variables
		155	$SIG{KILL} = sub { };
		156
102	our $VERSION = '0.041';	157	our $VERSION = '0.6';
103		158
104	require XSLoader;	159	require XSLoader;
105	XSLoader::load Async::Interrupt::, $VERSION;	160	XSLoader::load ("Async::Interrupt", $VERSION);
106	}	161	}
107		162
108	our $DIED = sub { warn "$@" };	163	our $DIED = sub { warn "$@" };
109		164
110	=item $async = new Async::Interrupt key => value...	165	=item $async = new Async::Interrupt key => value...
…		…
153	might use (the exception is C<errno>, which is saved and restored by	208	might use (the exception is C<errno>, which is saved and restored by
154	Async::Interrupt). The callback itself runs as part of the perl context,	209	Async::Interrupt). The callback itself runs as part of the perl context,
155	so you can call any perl functions and modify any perl data structures (in	210	so you can call any perl functions and modify any perl data structures (in
156	which case the requirements set out for C<cb> apply as well).	211	which case the requirements set out for C<cb> apply as well).
157		212
		213	=item var => $scalar_ref
		214
		215	When specified, then the given argument must be a reference to a
		216	scalar. The scalar will be set to C<0> initially. Signalling the interrupt
		217	object will set it to the passed value, handling the interrupt will reset
		218	it to C<0> again.
		219
		220	Note that the only thing you are legally allowed to do is to is to check
		221	the variable in a boolean or integer context (e.g. comparing it with a
		222	string, or printing it, will I<destroy> it and might cause your program to
		223	crash or worse).
		224
158	=item signal => $signame_or_value	225	=item signal => $signame_or_value
159		226
160	When this parameter is specified, then the Async::Interrupt will hook the	227	When this parameter is specified, then the Async::Interrupt will hook the
161	given signal, that is, it will effectively call C<< ->signal (0) >> each time	228	given signal, that is, it will effectively call C<< ->signal (0) >> each time
162	the given signal is caught by the process.	229	the given signal is caught by the process.
…		…
171	be written to it, and before the callback is being invoked, it will be	238	be written to it, and before the callback is being invoked, it will be
172	read again. Due to races, it is unlikely but possible that multiple octets	239	read again. Due to races, it is unlikely but possible that multiple octets
173	are written. It is required that the file handles are both in nonblocking	240	are written. It is required that the file handles are both in nonblocking
174	mode.	241	mode.
175		242
176	You can get a portable pipe and set non-blocking mode portably by using
177	e.g. L<AnyEvent::Util> from the L<AnyEvent> distribution.
178
179	It is also possible to pass in a linux eventfd as both read and write
180	handle (which is faster than a pipe).
181
182	The object will keep a reference to the file handles.	243	The object will keep a reference to the file handles.
183		244
184	This can be used to ensure that async notifications will interrupt event	245	This can be used to ensure that async notifications will interrupt event
185	frameworks as well.	246	frameworks as well.
186		247
		248	Note that C<Async::Interrupt> will create a suitable signal fd
		249	automatically when your program requests one, so you don't have to specify
		250	this argument when all you want is an extra file descriptor to watch.
		251
		252	If you want to share a single event pipe between multiple Async::Interrupt
		253	objects, you can use the C<Async::Interrupt::EventPipe> class to manage
		254	those.
		255
187	=back	256	=back
188		257
189	=cut	258	=cut
190		259
191	sub new {	260	sub new {
192	my ($class, %arg) = @_;	261	my ($class, %arg) = @_;
193		262
194	bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}), $class	263	bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class
195	}	264	}
196		265
197	=item ($signal_func, $signal_arg) = $async->signal_func	266	=item ($signal_func, $signal_arg) = $async->signal_func
198		267
199	Returns the address of a function to call asynchronously. The function has	268	Returns the address of a function to call asynchronously. The function
200	the following prototype and needs to be passed the specified C<$c_arg>,	269	has the following prototype and needs to be passed the specified
201	which is a C<void *> cast to C<IV>:	270	C<$signal_arg>, which is a C<void *> cast to C<IV>:
202		271
203	void (signal_func) (void signal_arg, int value)	272	void (signal_func) (void signal_arg, int value)
204		273
205	An example call would look like:	274	An example call would look like:
206		275
207	signal_func (signal_arg, 0);	276	signal_func (signal_arg, 0);
208		277
209	The function is safe to call from within signal and thread contexts, at	278	The function is safe to call from within signal and thread contexts, at
210	any time. The specified C<value> is passed to both C and Perl callback.	279	any time. The specified C<value> is passed to both C and Perl callback.
211		280
212	C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is	281	C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0>
213	portable).	282	(1..127 is portable).
214		283
215	If the function is called while the Async::Interrupt object is already	284	If the function is called while the Async::Interrupt object is already
216	signaled but before the callbacks are being executed, then the stored	285	signaled but before the callbacks are being executed, then the stored
217	C<value> is either the old or the new one. Due to the asynchronous	286	C<value> is either the old or the new one. Due to the asynchronous
218	nature of the code, the C<value> can even be passed to two consecutive	287	nature of the code, the C<value> can even be passed to two consecutive
219	invocations of the callback.	288	invocations of the callback.
220		289
		290	=item $address = $async->c_var
		291
		292	Returns the address (cast to IV) of an C<IV> variable. The variable is set
		293	to C<0> initially and gets set to the passed value whenever the object
		294	gets signalled, and reset to C<0> once the interrupt has been handled.
		295
		296	Note that it is often beneficial to just call C<PERL_ASYNC_CHECK ()> to
		297	handle any interrupts.
		298
		299	Example: call some XS function to store the address, then show C code
		300	waiting for it.
		301
		302	my_xs_func $async->c_var;
		303
		304	static IV *valuep;
		305
		306	void
		307	my_xs_func (void *addr)
		308	CODE:
		309	valuep = (IV *)addr;
		310
		311	// code in a loop, waiting
		312	while (!*valuep)
		313	; // do something
		314
221	=item $async->signal ($value=0)	315	=item $async->signal ($value=1)
222		316
223	This signals the given async object from Perl code. Semi-obviously, this	317	This signals the given async object from Perl code. Semi-obviously, this
224	will instantly trigger the callback invocation.	318	will instantly trigger the callback invocation (it does not, as the name
		319	might imply, do anything with POSIX signals).
225		320
226	C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is	321	C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0>
227	portable).	322	(1..127 is portable).
		323
		324	=item $async->signal_hysteresis ($enable)
		325
		326	Enables or disables signal hysteresis (default: disabled). If a POSIX
		327	signal is used as a signal source for the interrupt object, then enabling
		328	signal hysteresis causes Async::Interrupt to reset the signal action to
		329	C<SIG_IGN> in the signal handler and restore it just before handling the
		330	interruption.
		331
		332	When you expect a lot of signals (e.g. when using SIGIO), then enabling
		333	signal hysteresis can reduce the number of handler invocations
		334	considerably, at the cost of two extra syscalls.
		335
		336	Note that setting the signal to C<SIG_IGN> can have unintended side
		337	effects when you fork and exec other programs, as often they do nto expect
		338	signals to be ignored by default.
228		339
229	=item $async->block	340	=item $async->block
230		341
231	=item $async->unblock	342	=item $async->unblock
232		343
…		…
247	This call C<< $async->block >> and installs a handler that is called when	358	This call C<< $async->block >> and installs a handler that is called when
248	the current scope is exited (via an exception, by canceling the Coro	359	the current scope is exited (via an exception, by canceling the Coro
249	thread, by calling last/goto etc.).	360	thread, by calling last/goto etc.).
250		361
251	This is the recommended (and fastest) way to implement critical sections.	362	This is the recommended (and fastest) way to implement critical sections.
		363
		364	=item ($block_func, $block_arg) = $async->scope_block_func
		365
		366	Returns the address of a function that implements the C<scope_block>
		367	functionality.
		368
		369	It has the following prototype and needs to be passed the specified
		370	C<$block_arg>, which is a C<void *> cast to C<IV>:
		371
		372	void (block_func) (void block_arg)
		373
		374	An example call would look like:
		375
		376	block_func (block_arg);
		377
		378	The function is safe to call only from within the toplevel of a perl XS
		379	function and will call C<LEAVE> and C<ENTER> (in this order!).
252		380
253	=item $async->pipe_enable	381	=item $async->pipe_enable
254		382
255	=item $async->pipe_disable	383	=item $async->pipe_disable
256		384
…		…
258	enabled). Writing to a pipe is relatively expensive, so it can be disabled	386	enabled). Writing to a pipe is relatively expensive, so it can be disabled
259	when you know you are not waiting for it (for example, with L<EV> you	387	when you know you are not waiting for it (for example, with L<EV> you
260	could disable the pipe in a check watcher, and enable it in a prepare	388	could disable the pipe in a check watcher, and enable it in a prepare
261	watcher).	389	watcher).
262		390
263	Note that when C<fd_disable> is in effect, no attempt to read from the	391	Note that currently, while C<pipe_disable> is in effect, no attempt to
264	pipe will be done.	392	read from the pipe will be done when handling events. This might change as
		393	soon as I realize why this is a mistake.
		394
		395	=item $fileno = $async->pipe_fileno
		396
		397	Returns the reading side of the signalling pipe. If no signalling pipe is
		398	currently attached to the object, it will dynamically create one.
		399
		400	Note that the only valid oepration on this file descriptor is to wait
		401	until it is readable. The fd might belong currently to a pipe, a tcp
		402	socket, or an eventfd, depending on the platform, and is guaranteed to be
		403	C<select>able.
		404
		405	=item $async->pipe_autodrain ($enable)
		406
		407	Enables (C<1>) or disables (C<0>) automatic draining of the pipe (default:
		408	enabled). When automatic draining is enabled, then Async::Interrupt will
		409	automatically clear the pipe. Otherwise the user is responsible for this
		410	draining.
		411
		412	This is useful when you want to share one pipe among many Async::Interrupt
		413	objects.
		414
		415	=item $async->post_fork
		416
		417	The object will not normally be usable after a fork (as the pipe fd is
		418	shared between processes). Calling this method after a fork in the child
		419	ensures that the object will work as expected again. It only needs to be
		420	called when the async object is used in the child.
		421
		422	This only works when the pipe was created by Async::Interrupt.
		423
		424	Async::Interrupt ensures that the reading file descriptor does not change
		425	it's value.
		426
		427	=item $signum = Async::Interrupt::sig2num $signame_or_number
		428
		429	=item $signame = Async::Interrupt::sig2name $signame_or_number
		430
		431	These two convenience functions simply convert a signal name or number to
		432	the corresponding name or number. They are not used by this module and
		433	exist just because perl doesn't have a nice way to do this on its own.
		434
		435	They will return C<undef> on illegal names or numbers.
		436
		437	=back
		438
		439	=head1 THE Async::Interrupt::EventPipe CLASS
		440
		441	Pipes are the predominent utility to make asynchronous signals
		442	synchronous. However, pipes are hard to come by: they don't exist on the
		443	broken windows platform, and on GNU/Linux systems, you might want to use
		444	an C<eventfd> instead.
		445
		446	This class creates selectable event pipes in a portable fashion: on
		447	windows, it will try to create a tcp socket pair, on GNU/Linux, it will
		448	try to create an eventfd and everywhere else it will try to use a normal
		449	pipe.
		450
		451	=over 4
		452
		453	=item $epipe = new Async::Interrupt::EventPipe
		454
		455	This creates and returns an eventpipe object. This object is simply a
		456	blessed array reference:
		457
		458	=item ($r_fd, $w_fd) = $epipe->filenos
		459
		460	Returns the read-side file descriptor and the write-side file descriptor.
		461
		462	Example: pass an eventpipe object as pipe to the Async::Interrupt
		463	constructor, and create an AnyEvent watcher for the read side.
		464
		465	my $epipe = new Async::Interrupt::EventPipe;
		466	my $asy = new Async::Interrupt pipe => [$epipe->filenos];
		467	my $iow = AnyEvent->io (fh => $epipe->fileno, poll => 'r', cb => sub { });
		468
		469	=item $r_fd = $epipe->fileno
		470
		471	Return only the reading/listening side.
		472
		473	=item $epipe->signal
		474
		475	Write something to the pipe, in a portable fashion.
		476
		477	=item $epipe->drain
		478
		479	Drain (empty) the pipe.
		480
		481	=item $epipe->renew
		482
		483	Recreates the pipe (useful after a fork). The reading side will not change
		484	it's file descriptor number, but the writing side might.
		485
		486	=back
265		487
266	=cut	488	=cut
267		489
268	1;	490	1;
269
270	=back
271		491
272	=head1 EXAMPLE	492	=head1 EXAMPLE
273		493
274	There really should be a complete C/XS example. Bug me about it. Better	494	There really should be a complete C/XS example. Bug me about it. Better
275	yet, create one.	495	yet, create one.
…		…
283	then intercepts the interpreter handling it. This makes normal signal	503	then intercepts the interpreter handling it. This makes normal signal
284	handling slower (probably unmeasurably, though), but has the advantage	504	handling slower (probably unmeasurably, though), but has the advantage
285	of not requiring a special runops function, nor slowing down normal perl	505	of not requiring a special runops function, nor slowing down normal perl
286	execution a bit.	506	execution a bit.
287		507
288	It assumes that C<sig_atomic_t> and C<int> are both async-safe to modify	508	It assumes that C<sig_atomic_t>, C<int> and C<IV> are all async-safe to
289	(C<sig_atomic_> is used by this module, and perl itself uses C<int>, so we	509	modify.
290	can assume that this is quite portable, at least w.r.t. signals).
291		510
292	=head1 AUTHOR	511	=head1 AUTHOR
293		512
294	Marc Lehmann <schmorp@schmorp.de>	513	Marc Lehmann <schmorp@schmorp.de>
295	http://home.schmorp.de/	514	http://home.schmorp.de/

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Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents): Revision 1.10 by root, Sun Jul 12 23:03:36 2009 UTC vs. Revision 1.18 by root, Tue Jul 28 12:50:16 2009 UTC

Diff Legend

Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents):
Revision 1.10 by root, Sun Jul 12 23:03:36 2009 UTC vs.
Revision 1.18 by root, Tue Jul 28 12:50:16 2009 UTC