[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 1.19 by root, Tue Jul 28 13:17:05 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 Implementing race-free signal handling
		99
		100	This example uses a single event pipe for all signals, and one
		101	Async::Interrupt per signal. This code is actually what the L<AnyEvent>
		102	module uses itself when Async::Interrupt is available.
		103
		104	First, create the event pipe and hook it into the event loop
		105
		106	$SIGPIPE = new Async::Interrupt::EventPipe;
		107	$SIGPIPE_W = AnyEvent->io (
		108	fh => $SIGPIPE->fileno,
		109	poll => "r",
		110	cb => \&_signal_check, # defined later
		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 => $signum,
		121	pipe => [$SIGPIPE->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	=head2 Interrupt perl from another thread
		141
		142	This example interrupts the Perl interpreter from another thread, via the
		143	XS API. This is used by e.g. the L<EV::Loop::Async> module.
		144
		145	#TODO#
		146
		147	=head1 THE Async::Interrupt CLASS
		148
93	=over 4	149	=over 4
94		150
95	=cut	151	=cut
96		152
97	package Async::Interrupt;	153	package Async::Interrupt;
98		154
99	use common::sense;	155	use common::sense;
100		156
101	BEGIN {	157	BEGIN {
102	# the next line forces initialisation of internal	158	# the next line forces initialisation of internal
103	# signal handling # variables	159	# signal handling variables, otherwise, PL_sig_pending
		160	# etc. will be null pointers.
104	$SIG{KILL} = sub { };	161	$SIG{KILL} = sub { };
105		162
106	our $VERSION = '0.042';	163	our $VERSION = '1.0';
107		164
108	require XSLoader;	165	require XSLoader;
109	XSLoader::load ("Async::Interrupt", $VERSION);	166	XSLoader::load ("Async::Interrupt", $VERSION);
110	}	167	}
111		168
…		…
134	The exceptions are C<$!> and C<$@>, which are saved and restored by	191	The exceptions are C<$!> and C<$@>, which are saved and restored by
135	Async::Interrupt.	192	Async::Interrupt.
136		193
137	If the callback should throw an exception, then it will be caught,	194	If the callback should throw an exception, then it will be caught,
138	and C<$Async::Interrupt::DIED> will be called with C<$@> containing	195	and C<$Async::Interrupt::DIED> will be called with C<$@> containing
139	the exception. The default will simply C<warn> about the message and	196	the exception. The default will simply C<warn> about the message and
140	continue.	197	continue.
141		198
142	=item c_cb => [$c_func, $c_arg]	199	=item c_cb => [$c_func, $c_arg]
143		200
144	Registers a C callback the be invoked whenever the async interrupt is	201	Registers a C callback the be invoked whenever the async interrupt is
…		…
157	might use (the exception is C<errno>, which is saved and restored by	214	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,	215	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	216	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).	217	which case the requirements set out for C<cb> apply as well).
161		218
		219	=item var => $scalar_ref
		220
		221	When specified, then the given argument must be a reference to a
		222	scalar. The scalar will be set to C<0> initially. Signalling the interrupt
		223	object will set it to the passed value, handling the interrupt will reset
		224	it to C<0> again.
		225
		226	Note that the only thing you are legally allowed to do is to is to check
		227	the variable in a boolean or integer context (e.g. comparing it with a
		228	string, or printing it, will I<destroy> it and might cause your program to
		229	crash or worse).
		230
162	=item signal => $signame_or_value	231	=item signal => $signame_or_value
163		232
164	When this parameter is specified, then the Async::Interrupt will hook the	233	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	234	given signal, that is, it will effectively call C<< ->signal (0) >> each time
166	the given signal is caught by the process.	235	the given signal is caught by the process.
167		236
168	Only one async can hook a given signal, and the signal will be restored to	237	Only one async can hook a given signal, and the signal will be restored to
169	defaults when the Async::Interrupt object gets destroyed.	238	defaults when the Async::Interrupt object gets destroyed.
		239
		240	=item signal_hysteresis => $boolean
		241
		242	Sets the initial signal hysteresis state, see the C<signal_hysteresis>
		243	method, below.
170		244
171	=item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing]	245	=item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing]
172		246
173	Specifies two file descriptors (or file handles) that should be signalled	247	Specifies two file descriptors (or file handles) that should be signalled
174	whenever the async interrupt is signalled. This means a single octet will	248	whenever the async interrupt is signalled. This means a single octet will
175	be written to it, and before the callback is being invoked, it will be	249	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	250	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	251	are written. It is required that the file handles are both in nonblocking
178	mode.	252	mode.
179		253
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.	254	The object will keep a reference to the file handles.
187		255
188	This can be used to ensure that async notifications will interrupt event	256	This can be used to ensure that async notifications will interrupt event
189	frameworks as well.	257	frameworks as well.
190		258
		259	Note that C<Async::Interrupt> will create a suitable signal fd
		260	automatically when your program requests one, so you don't have to specify
		261	this argument when all you want is an extra file descriptor to watch.
		262
		263	If you want to share a single event pipe between multiple Async::Interrupt
		264	objects, you can use the C<Async::Interrupt::EventPipe> class to manage
		265	those.
		266
		267	=item pipe_autodrain => $boolean
		268
		269	Sets the initial autodrain state, see the C<pipe_autodrain> method, below.
		270
191	=back	271	=back
192		272
193	=cut	273	=cut
194		274
195	sub new {	275	sub new {
196	my ($class, %arg) = @_;	276	my ($class, %arg) = @_;
197		277
198	bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}), $class	278	my $self = bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class;
		279
		280	# urgs, reminds me of Event
		281	for my $attr (qw(pipe_autodrain signal_hysteresis)) {
		282	$self->$attr ($arg{$attr}) if exists $arg{$attr};
		283	}
		284
		285	$self
199	}	286	}
200		287
201	=item ($signal_func, $signal_arg) = $async->signal_func	288	=item ($signal_func, $signal_arg) = $async->signal_func
202		289
203	Returns the address of a function to call asynchronously. The function has	290	Returns the address of a function to call asynchronously. The function
204	the following prototype and needs to be passed the specified C<$c_arg>,	291	has the following prototype and needs to be passed the specified
205	which is a C<void *> cast to C<IV>:	292	C<$signal_arg>, which is a C<void *> cast to C<IV>:
206		293
207	void (signal_func) (void signal_arg, int value)	294	void (signal_func) (void signal_arg, int value)
208		295
209	An example call would look like:	296	An example call would look like:
210		297
211	signal_func (signal_arg, 0);	298	signal_func (signal_arg, 0);
212		299
213	The function is safe to call from within signal and thread contexts, at	300	The function is safe to call from within signal and thread contexts, at
214	any time. The specified C<value> is passed to both C and Perl callback.	301	any time. The specified C<value> is passed to both C and Perl callback.
215		302
216	C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is	303	C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0>
217	portable).	304	(1..127 is portable).
218		305
219	If the function is called while the Async::Interrupt object is already	306	If the function is called while the Async::Interrupt object is already
220	signaled but before the callbacks are being executed, then the stored	307	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	308	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	309	nature of the code, the C<value> can even be passed to two consecutive
223	invocations of the callback.	310	invocations of the callback.
224		311
		312	=item $address = $async->c_var
		313
		314	Returns the address (cast to IV) of an C<IV> variable. The variable is set
		315	to C<0> initially and gets set to the passed value whenever the object
		316	gets signalled, and reset to C<0> once the interrupt has been handled.
		317
		318	Note that it is often beneficial to just call C<PERL_ASYNC_CHECK ()> to
		319	handle any interrupts.
		320
		321	Example: call some XS function to store the address, then show C code
		322	waiting for it.
		323
		324	my_xs_func $async->c_var;
		325
		326	static IV *valuep;
		327
		328	void
		329	my_xs_func (void *addr)
		330	CODE:
		331	valuep = (IV *)addr;
		332
		333	// code in a loop, waiting
		334	while (!*valuep)
		335	; // do something
		336
225	=item $async->signal ($value=0)	337	=item $async->signal ($value=1)
226		338
227	This signals the given async object from Perl code. Semi-obviously, this	339	This signals the given async object from Perl code. Semi-obviously, this
228	will instantly trigger the callback invocation.	340	will instantly trigger the callback invocation (it does not, as the name
		341	might imply, do anything with POSIX signals).
229		342
230	C<$value> must be in the valid range for a C<sig_atomic_t> (0..127 is	343	C<$value> must be in the valid range for a C<sig_atomic_t>, except C<0>
231	portable).	344	(1..127 is portable).
		345
		346	=item $async->signal_hysteresis ($enable)
		347
		348	Enables or disables signal hysteresis (default: disabled). If a POSIX
		349	signal is used as a signal source for the interrupt object, then enabling
		350	signal hysteresis causes Async::Interrupt to reset the signal action to
		351	C<SIG_IGN> in the signal handler and restore it just before handling the
		352	interruption.
		353
		354	When you expect a lot of signals (e.g. when using SIGIO), then enabling
		355	signal hysteresis can reduce the number of handler invocations
		356	considerably, at the cost of two extra syscalls.
		357
		358	Note that setting the signal to C<SIG_IGN> can have unintended side
		359	effects when you fork and exec other programs, as often they do nto expect
		360	signals to be ignored by default.
232		361
233	=item $async->block	362	=item $async->block
234		363
235	=item $async->unblock	364	=item $async->unblock
236		365
…		…
251	This call C<< $async->block >> and installs a handler that is called when	380	This call C<< $async->block >> and installs a handler that is called when
252	the current scope is exited (via an exception, by canceling the Coro	381	the current scope is exited (via an exception, by canceling the Coro
253	thread, by calling last/goto etc.).	382	thread, by calling last/goto etc.).
254		383
255	This is the recommended (and fastest) way to implement critical sections.	384	This is the recommended (and fastest) way to implement critical sections.
		385
		386	=item ($block_func, $block_arg) = $async->scope_block_func
		387
		388	Returns the address of a function that implements the C<scope_block>
		389	functionality.
		390
		391	It has the following prototype and needs to be passed the specified
		392	C<$block_arg>, which is a C<void *> cast to C<IV>:
		393
		394	void (block_func) (void block_arg)
		395
		396	An example call would look like:
		397
		398	block_func (block_arg);
		399
		400	The function is safe to call only from within the toplevel of a perl XS
		401	function and will call C<LEAVE> and C<ENTER> (in this order!).
256		402
257	=item $async->pipe_enable	403	=item $async->pipe_enable
258		404
259	=item $async->pipe_disable	405	=item $async->pipe_disable
260		406
…		…
262	enabled). Writing to a pipe is relatively expensive, so it can be disabled	408	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	409	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	410	could disable the pipe in a check watcher, and enable it in a prepare
265	watcher).	411	watcher).
266		412
267	Note that when C<fd_disable> is in effect, no attempt to read from the	413	Note that currently, while C<pipe_disable> is in effect, no attempt to
268	pipe will be done.	414	read from the pipe will be done when handling events. This might change as
		415	soon as I realize why this is a mistake.
		416
		417	=item $fileno = $async->pipe_fileno
		418
		419	Returns the reading side of the signalling pipe. If no signalling pipe is
		420	currently attached to the object, it will dynamically create one.
		421
		422	Note that the only valid oepration on this file descriptor is to wait
		423	until it is readable. The fd might belong currently to a pipe, a tcp
		424	socket, or an eventfd, depending on the platform, and is guaranteed to be
		425	C<select>able.
		426
		427	=item $async->pipe_autodrain ($enable)
		428
		429	Enables (C<1>) or disables (C<0>) automatic draining of the pipe (default:
		430	enabled). When automatic draining is enabled, then Async::Interrupt will
		431	automatically clear the pipe. Otherwise the user is responsible for this
		432	draining.
		433
		434	This is useful when you want to share one pipe among many Async::Interrupt
		435	objects.
		436
		437	=item $async->post_fork
		438
		439	The object will not normally be usable after a fork (as the pipe fd is
		440	shared between processes). Calling this method after a fork in the child
		441	ensures that the object will work as expected again. It only needs to be
		442	called when the async object is used in the child.
		443
		444	This only works when the pipe was created by Async::Interrupt.
		445
		446	Async::Interrupt ensures that the reading file descriptor does not change
		447	it's value.
		448
		449	=item $signum = Async::Interrupt::sig2num $signame_or_number
		450
		451	=item $signame = Async::Interrupt::sig2name $signame_or_number
		452
		453	These two convenience functions simply convert a signal name or number to
		454	the corresponding name or number. They are not used by this module and
		455	exist just because perl doesn't have a nice way to do this on its own.
		456
		457	They will return C<undef> on illegal names or numbers.
		458
		459	=back
		460
		461	=head1 THE Async::Interrupt::EventPipe CLASS
		462
		463	Pipes are the predominent utility to make asynchronous signals
		464	synchronous. However, pipes are hard to come by: they don't exist on the
		465	broken windows platform, and on GNU/Linux systems, you might want to use
		466	an C<eventfd> instead.
		467
		468	This class creates selectable event pipes in a portable fashion: on
		469	windows, it will try to create a tcp socket pair, on GNU/Linux, it will
		470	try to create an eventfd and everywhere else it will try to use a normal
		471	pipe.
		472
		473	=over 4
		474
		475	=item $epipe = new Async::Interrupt::EventPipe
		476
		477	This creates and returns an eventpipe object. This object is simply a
		478	blessed array reference:
		479
		480	=item ($r_fd, $w_fd) = $epipe->filenos
		481
		482	Returns the read-side file descriptor and the write-side file descriptor.
		483
		484	Example: pass an eventpipe object as pipe to the Async::Interrupt
		485	constructor, and create an AnyEvent watcher for the read side.
		486
		487	my $epipe = new Async::Interrupt::EventPipe;
		488	my $asy = new Async::Interrupt pipe => [$epipe->filenos];
		489	my $iow = AnyEvent->io (fh => $epipe->fileno, poll => 'r', cb => sub { });
		490
		491	=item $r_fd = $epipe->fileno
		492
		493	Return only the reading/listening side.
		494
		495	=item $epipe->signal
		496
		497	Write something to the pipe, in a portable fashion.
		498
		499	=item $epipe->drain
		500
		501	Drain (empty) the pipe.
		502
		503	=item $epipe->renew
		504
		505	Recreates the pipe (useful after a fork). The reading side will not change
		506	it's file descriptor number, but the writing side might.
		507
		508	=back
269		509
270	=cut	510	=cut
271		511
272	1;	512	1;
273
274	=back
275		513
276	=head1 EXAMPLE	514	=head1 EXAMPLE
277		515
278	There really should be a complete C/XS example. Bug me about it. Better	516	There really should be a complete C/XS example. Bug me about it. Better
279	yet, create one.	517	yet, create one.
…		…
287	then intercepts the interpreter handling it. This makes normal signal	525	then intercepts the interpreter handling it. This makes normal signal
288	handling slower (probably unmeasurably, though), but has the advantage	526	handling slower (probably unmeasurably, though), but has the advantage
289	of not requiring a special runops function, nor slowing down normal perl	527	of not requiring a special runops function, nor slowing down normal perl
290	execution a bit.	528	execution a bit.
291		529
292	It assumes that C<sig_atomic_t> and C<int> are both async-safe to modify	530	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	531	modify.
294	can assume that this is quite portable, at least w.r.t. signals).
295		532
296	=head1 AUTHOR	533	=head1 AUTHOR
297		534
298	Marc Lehmann <schmorp@schmorp.de>	535	Marc Lehmann <schmorp@schmorp.de>
299	http://home.schmorp.de/	536	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 1.19 by root, Tue Jul 28 13:17:05 2009 UTC

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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 1.19 by root, Tue Jul 28 13:17:05 2009 UTC