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

Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents):
Revision 1.12 by root, Tue Jul 14 19:51:24 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;
…		…
101	BEGIN {	152	BEGIN {
102	# the next line forces initialisation of internal	153	# the next line forces initialisation of internal
103	# signal handling # variables	154	# signal handling # variables
104	$SIG{KILL} = sub { };	155	$SIG{KILL} = sub { };
105		156
106	our $VERSION = '0.042';	157	our $VERSION = '0.6';
107		158
108	require XSLoader;	159	require XSLoader;
109	XSLoader::load ("Async::Interrupt", $VERSION);	160	XSLoader::load ("Async::Interrupt", $VERSION);
110	}	161	}
111		162
…		…
157	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
158	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,
159	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
160	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).
161		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
162	=item signal => $signame_or_value	225	=item signal => $signame_or_value
163		226
164	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
165	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
166	the given signal is caught by the process.	229	the given signal is caught by the process.
…		…
175	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
176	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
177	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
178	mode.	241	mode.
179		242
180	You can get a portable pipe and set non-blocking mode portably by using
181	e.g. L<AnyEvent::Util> from the L<AnyEvent> distribution.
182
183	It is also possible to pass in a linux eventfd as both read and write
184	handle (which is faster than a pipe).
185
186	The object will keep a reference to the file handles.	243	The object will keep a reference to the file handles.
187		244
188	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
189	frameworks as well.	246	frameworks as well.
190		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
191	=back	256	=back
192		257
193	=cut	258	=cut
194		259
195	sub new {	260	sub new {
196	my ($class, %arg) = @_;	261	my ($class, %arg) = @_;
197		262
198	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}), $class
199	}	264	}
200		265
201	=item ($signal_func, $signal_arg) = $async->signal_func	266	=item ($signal_func, $signal_arg) = $async->signal_func
202		267
203	Returns the address of a function to call asynchronously. The function has	268	Returns the address of a function to call asynchronously. The function
204	the following prototype and needs to be passed the specified C<$c_arg>,	269	has the following prototype and needs to be passed the specified
205	which is a C<void *> cast to C<IV>:	270	C<$signal_arg>, which is a C<void *> cast to C<IV>:
206		271
207	void (signal_func) (void signal_arg, int value)	272	void (signal_func) (void signal_arg, int value)
208		273
209	An example call would look like:	274	An example call would look like:
210		275
211	signal_func (signal_arg, 0);	276	signal_func (signal_arg, 0);
212		277
213	The function is safe to call from within signal and thread contexts, at	278	The function is safe to call from within signal and thread contexts, at
214	any time. The specified C<value> is passed to both C and Perl callback.	279	any time. The specified C<value> is passed to both C and Perl callback.
215		280
216	C<$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>
217	portable).	282	(1..127 is portable).
218		283
219	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
220	signaled but before the callbacks are being executed, then the stored	285	signaled but before the callbacks are being executed, then the stored
221	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
222	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
223	invocations of the callback.	288	invocations of the callback.
224		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
225	=item $async->signal ($value=0)	315	=item $async->signal ($value=1)
226		316
227	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
228	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).
229		320
230	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>
231	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.
232		339
233	=item $async->block	340	=item $async->block
234		341
235	=item $async->unblock	342	=item $async->unblock
236		343
…		…
251	This call C<< $async->block >> and installs a handler that is called when	358	This call C<< $async->block >> and installs a handler that is called when
252	the current scope is exited (via an exception, by canceling the Coro	359	the current scope is exited (via an exception, by canceling the Coro
253	thread, by calling last/goto etc.).	360	thread, by calling last/goto etc.).
254		361
255	This is the recommended (and fastest) way to implement critical sections.	362	This is the recommended (and fastest) way to implement critical sections.
		363
		364	=item ($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!).
256		380
257	=item $async->pipe_enable	381	=item $async->pipe_enable
258		382
259	=item $async->pipe_disable	383	=item $async->pipe_disable
260		384
…		…
262	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
263	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
264	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
265	watcher).	389	watcher).
266		390
267	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
268	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
269		487
270	=cut	488	=cut
271		489
272	1;	490	1;
273
274	=back
275		491
276	=head1 EXAMPLE	492	=head1 EXAMPLE
277		493
278	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
279	yet, create one.	495	yet, create one.
…		…
287	then intercepts the interpreter handling it. This makes normal signal	503	then intercepts the interpreter handling it. This makes normal signal
288	handling slower (probably unmeasurably, though), but has the advantage	504	handling slower (probably unmeasurably, though), but has the advantage
289	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
290	execution a bit.	506	execution a bit.
291		507
292	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
293	(C<sig_atomic_> is used by this module, and perl itself uses C<int>, so we	509	modify.
294	can assume that this is quite portable, at least w.r.t. signals).
295		510
296	=head1 AUTHOR	511	=head1 AUTHOR
297		512
298	Marc Lehmann <schmorp@schmorp.de>	513	Marc Lehmann <schmorp@schmorp.de>
299	http://home.schmorp.de/	514	http://home.schmorp.de/

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Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents): Revision 1.12 by root, Tue Jul 14 19:51:24 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 1.12 by root, Tue Jul 14 19:51:24 2009 UTC vs.
Revision 1.18 by root, Tue Jul 28 12:50:16 2009 UTC