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

Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents):
Revision 1.17 by root, Tue Jul 28 01:19:44 2009 UTC vs.
Revision 1.22 by root, Wed Aug 5 11:51:53 2009 UTC

…		…
91	I<running> interpreter, there is optional support for signalling a pipe	91	I<running> interpreter, there is optional support for signalling a pipe
92	- 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
93	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>
94	and C<write> syscall.	94	and C<write> syscall.
95		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	On the Perl level, a new loop object (which contains the thread)
		146	is created, by first calling some XS constructor, querying the
		147	C-level callback function and feeding that as the C<c_cb> into the
		148	Async::Interrupt constructor:
		149
		150	my $self = XS_thread_constructor;
		151	my ($c_func, $c_arg) = _c_func $self; # return the c callback
		152	my $asy = new Async::Interrupt c_cb => [$c_func, $c_arg];
		153
		154	Then the newly created Interrupt object is queried for the signaling
		155	function that the newly created thread should call, and this is in turn
		156	told to the thread object:
		157
		158	_attach $self, $asy->signal_func;
		159
		160	So to repeat: first the XS object is created, then it is queried for the
		161	callback that should be called when the Interrupt object gets signalled.
		162
		163	Then the interrupt object is queried for the callback fucntion that the
		164	thread should call to signal the Interrupt object, and this callback is
		165	then attached to the thread.
		166
		167	You have to be careful that your new thread is not signalling before the
		168	signal function was configured, for example by starting the background
		169	thread only within C<_attach>.
		170
		171	That concludes the Perl part.
		172
		173	The XS part consists of the actual constructor which creates a thread,
		174	which is not relevant for this example, and two functions, C<_c_func>,
		175	which returns the Perl-side callback, and C<_attach>, which configures
		176	the signalling functioon that is safe toc all from another thread. For
		177	simplicity, we will use global variables to store the functions, normally
		178	you would somehow attach them to C<$self>.
		179
		180	The C<c_func> simply returns the address of a static function and arranges
		181	for the object pointed to by C<$self> to be passed to it, as an integer:
		182
		183	void
		184	_c_func (SV *loop)
		185	PPCODE:
		186	EXTEND (SP, 2);
		187	PUSHs (sv_2mortal (newSViv (PTR2IV (c_func))));
		188	PUSHs (sv_2mortal (newSViv (SvRV (loop))));
		189
		190	This would be the callback (since it runs in a normal Perl context, it is
		191	permissible to manipulate Perl values):
		192
		193	static void
		194	c_func (pTHX_ void *loop_, int value)
		195	{
		196	SV loop_object = (SV )loop_;
		197	...
		198	}
		199
		200	And this attaches the signalling callback:
		201
		202	static void (my_sig_func) (void signal_arg, int value);
		203	static void *my_sig_arg;
		204
		205	void
		206	_attach (SV loop_, IV sig_func, void sig_arg)
		207	CODE:
		208	{
		209	my_sig_func = sig_func;
		210	my_sig_arg = sig_arg;
		211
		212	/* now run the thread */
		213	thread_create (&u->tid, l_run, 0);
		214	}
		215
		216	And C<l_run> (the background thread) would eventually call the signaling
		217	function:
		218
		219	my_sig_func (my_sig_arg, 0);
		220
		221	You can have a look at L<EV::Loop::Async> for an actual example using
		222	intra-thread communication, locking and so on.
		223
		224
96	=head1 THE Async::Interrupt CLASS	225	=head1 THE Async::Interrupt CLASS
97		226
98	=over 4	227	=over 4
99		228
100	=cut	229	=cut
…		…
103		232
104	use common::sense;	233	use common::sense;
105		234
106	BEGIN {	235	BEGIN {
107	# the next line forces initialisation of internal	236	# the next line forces initialisation of internal
108	# signal handling # variables	237	# signal handling variables, otherwise, PL_sig_pending
		238	# etc. will be null pointers.
109	$SIG{KILL} = sub { };	239	$SIG{KILL} = sub { };
110		240
111	our $VERSION = '0.6';	241	our $VERSION = '1.01';
112		242
113	require XSLoader;	243	require XSLoader;
114	XSLoader::load ("Async::Interrupt", $VERSION);	244	XSLoader::load ("Async::Interrupt", $VERSION);
115	}	245	}
116		246
…		…
139	The exceptions are C<$!> and C<$@>, which are saved and restored by	269	The exceptions are C<$!> and C<$@>, which are saved and restored by
140	Async::Interrupt.	270	Async::Interrupt.
141		271
142	If the callback should throw an exception, then it will be caught,	272	If the callback should throw an exception, then it will be caught,
143	and C<$Async::Interrupt::DIED> will be called with C<$@> containing	273	and C<$Async::Interrupt::DIED> will be called with C<$@> containing
144	the exception. The default will simply C<warn> about the message and	274	the exception. The default will simply C<warn> about the message and
145	continue.	275	continue.
146		276
147	=item c_cb => [$c_func, $c_arg]	277	=item c_cb => [$c_func, $c_arg]
148		278
149	Registers a C callback the be invoked whenever the async interrupt is	279	Registers a C callback the be invoked whenever the async interrupt is
…		…
183	the given signal is caught by the process.	313	the given signal is caught by the process.
184		314
185	Only one async can hook a given signal, and the signal will be restored to	315	Only one async can hook a given signal, and the signal will be restored to
186	defaults when the Async::Interrupt object gets destroyed.	316	defaults when the Async::Interrupt object gets destroyed.
187		317
		318	=item signal_hysteresis => $boolean
		319
		320	Sets the initial signal hysteresis state, see the C<signal_hysteresis>
		321	method, below.
		322
188	=item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing]	323	=item pipe => [$fileno_or_fh_for_reading, $fileno_or_fh_for_writing]
189		324
190	Specifies two file descriptors (or file handles) that should be signalled	325	Specifies two file descriptors (or file handles) that should be signalled
191	whenever the async interrupt is signalled. This means a single octet will	326	whenever the async interrupt is signalled. This means a single octet will
192	be written to it, and before the callback is being invoked, it will be	327	be written to it, and before the callback is being invoked, it will be
…		…
205		340
206	If you want to share a single event pipe between multiple Async::Interrupt	341	If you want to share a single event pipe between multiple Async::Interrupt
207	objects, you can use the C<Async::Interrupt::EventPipe> class to manage	342	objects, you can use the C<Async::Interrupt::EventPipe> class to manage
208	those.	343	those.
209		344
		345	=item pipe_autodrain => $boolean
		346
		347	Sets the initial autodrain state, see the C<pipe_autodrain> method, below.
		348
210	=back	349	=back
211		350
212	=cut	351	=cut
213		352
214	sub new {	353	sub new {
215	my ($class, %arg) = @_;	354	my ($class, %arg) = @_;
216		355
217	bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class	356	my $self = bless \(_alloc $arg{cb}, @{$arg{c_cb}}[0,1], @{$arg{pipe}}[0,1], $arg{signal}, $arg{var}), $class;
		357
		358	# urgs, reminds me of Event
		359	for my $attr (qw(pipe_autodrain signal_hysteresis)) {
		360	$self->$attr ($arg{$attr}) if exists $arg{$attr};
		361	}
		362
		363	$self
218	}	364	}
219		365
220	=item ($signal_func, $signal_arg) = $async->signal_func	366	=item ($signal_func, $signal_arg) = $async->signal_func
221		367
222	Returns the address of a function to call asynchronously. The function	368	Returns the address of a function to call asynchronously. The function
…		…
376	This only works when the pipe was created by Async::Interrupt.	522	This only works when the pipe was created by Async::Interrupt.
377		523
378	Async::Interrupt ensures that the reading file descriptor does not change	524	Async::Interrupt ensures that the reading file descriptor does not change
379	it's value.	525	it's value.
380		526
		527	=item $signum = Async::Interrupt::sig2num $signame_or_number
		528
		529	=item $signame = Async::Interrupt::sig2name $signame_or_number
		530
		531	These two convenience functions simply convert a signal name or number to
		532	the corresponding name or number. They are not used by this module and
		533	exist just because perl doesn't have a nice way to do this on its own.
		534
		535	They will return C<undef> on illegal names or numbers.
		536
381	=back	537	=back
382		538
383	=head1 THE Async::Interrupt::EventPipe CLASS	539	=head1 THE Async::Interrupt::EventPipe CLASS
384		540
385	Pipes are the predominent utility to make asynchronous signals	541	Pipes are the predominent utility to make asynchronous signals
…		…
420		576
421	=item $epipe->drain	577	=item $epipe->drain
422		578
423	Drain (empty) the pipe.	579	Drain (empty) the pipe.
424		580
		581	=item ($c_func, $c_arg) = $epipe->drain_func
		582
		583	Returns a function pointer and C<void *> argument that can be called to
		584	have the effect of C<< $epipe->drain >> on the XS level.
		585
		586	It has the following prototype and needs to be passed the specified
		587	C<$c_arg>, which is a C<void *> cast to C<IV>:
		588
		589	void (c_func) (void c_arg)
		590
		591	An example call would look like:
		592
		593	c_func (c_arg);
		594
425	=item $epipe->renew	595	=item $epipe->renew
426		596
427	Recreates the pipe (useful after a fork). The reading side will not change	597	Recreates the pipe (useful after a fork). The reading side will not change
428	it's file descriptor number, but the writing side might.	598	it's file descriptor number, but the writing side might.
429		599
		600	=item $epipe->wait
		601
		602	This method blocks the process until there are events on the pipe. This is
		603	not a very event-based or ncie way of usign an event pipe, but it can be
		604	occasionally useful.
		605
430	=back	606	=back
431		607
432	=cut	608	=cut
433		609
434	1;	610	1;
435
436	=head1 EXAMPLE
437
438	There really should be a complete C/XS example. Bug me about it. Better
439	yet, create one.
440		611
441	=head1 IMPLEMENTATION DETAILS AND LIMITATIONS	612	=head1 IMPLEMENTATION DETAILS AND LIMITATIONS
442		613
443	This module works by "hijacking" SIGKILL, which is guaranteed to always	614	This module works by "hijacking" SIGKILL, which is guaranteed to always
444	exist, but also cannot be caught, so is always available.	615	exist, but also cannot be caught, so is always available.

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Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents): Revision 1.17 by root, Tue Jul 28 01:19:44 2009 UTC vs. Revision 1.22 by root, Wed Aug 5 11:51:53 2009 UTC

Diff Legend

Comparing cvsroot/Async-Interrupt/Interrupt.pm (file contents):
Revision 1.17 by root, Tue Jul 28 01:19:44 2009 UTC vs.
Revision 1.22 by root, Wed Aug 5 11:51:53 2009 UTC