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Revision 1.56 by root, Thu Nov 19 01:55:57 2009 UTC vs.
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC

… …
391 correctly. 391 correctly.
392 392
393 Example: exit on SIGINT 393 Example: exit on SIGINT
394 394
395 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); 395 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
396
397 Restart Behaviour
398 While restart behaviour is up to the event loop implementation, most
399 will not restart syscalls (that includes Async::Interrupt and AnyEvent's
400 pure perl implementation).
401
402 Safe/Unsafe Signals
403 Perl signals can be either "safe" (synchronous to opcode handling) or
404 "unsafe" (asynchronous) - the former might get delayed indefinitely, the
405 latter might corrupt your memory.
406
407 AnyEvent signal handlers are, in addition, synchronous to the event
408 loop, i.e. they will not interrupt your running perl program but will
409 only be called as part of the normal event handling (just like timer,
410 I/O etc. callbacks, too).
396 411
397 Signal Races, Delays and Workarounds 412 Signal Races, Delays and Workarounds
398 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching 413 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
399 callbacks to signals in a generic way, which is a pity, as you cannot do 414 callbacks to signals in a generic way, which is a pity, as you cannot do
400 race-free signal handling in perl, requiring C libraries for this. 415 race-free signal handling in perl, requiring C libraries for this.
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1709 it's built-in modules) are required to use it. 1724 it's built-in modules) are required to use it.
1710 1725
1711 That does not mean that AnyEvent won't take advantage of some additional 1726 That does not mean that AnyEvent won't take advantage of some additional
1712 modules if they are installed. 1727 modules if they are installed.
1713 1728
1714 This section epxlains which additional modules will be used, and how 1729 This section explains which additional modules will be used, and how
1715 they affect AnyEvent's operetion. 1730 they affect AnyEvent's operation.
1716 1731
1717 Async::Interrupt 1732 Async::Interrupt
1718 This slightly arcane module is used to implement fast signal 1733 This slightly arcane module is used to implement fast signal
1719 handling: To my knowledge, there is no way to do completely 1734 handling: To my knowledge, there is no way to do completely
1720 race-free and quick signal handling in pure perl. To ensure that 1735 race-free and quick signal handling in pure perl. To ensure that
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1723 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). 1738 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1724 1739
1725 If this module is available, then it will be used to implement 1740 If this module is available, then it will be used to implement
1726 signal catching, which means that signals will not be delayed, and 1741 signal catching, which means that signals will not be delayed, and
1727 the event loop will not be interrupted regularly, which is more 1742 the event loop will not be interrupted regularly, which is more
1728 efficient (And good for battery life on laptops). 1743 efficient (and good for battery life on laptops).
1729 1744
1730 This affects not just the pure-perl event loop, but also other event 1745 This affects not just the pure-perl event loop, but also other event
1731 loops that have no signal handling on their own (e.g. Glib, Tk, Qt). 1746 loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1732 1747
1733 Some event loops (POE, Event, Event::Lib) offer signal watchers 1748 Some event loops (POE, Event, Event::Lib) offer signal watchers
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1775FORK 1790FORK
1776 Most event libraries are not fork-safe. The ones who are usually are 1791 Most event libraries are not fork-safe. The ones who are usually are
1777 because they rely on inefficient but fork-safe "select" or "poll" calls. 1792 because they rely on inefficient but fork-safe "select" or "poll" calls.
1778 Only EV is fully fork-aware. 1793 Only EV is fully fork-aware.
1779 1794
1795 This means that, in general, you cannot fork and do event processing in
1796 the child if a watcher was created before the fork (which in turn
1797 initialises the event library).
1798
1780 If you have to fork, you must either do so *before* creating your first 1799 If you have to fork, you must either do so *before* creating your first
1781 watcher OR you must not use AnyEvent at all in the child OR you must do 1800 watcher OR you must not use AnyEvent at all in the child OR you must do
1782 something completely out of the scope of AnyEvent. 1801 something completely out of the scope of AnyEvent.
1802
1803 The problem of doing event processing in the parent *and* the child is
1804 much more complicated: even for backends that *are* fork-aware or
1805 fork-safe, their behaviour is not usually what you want: fork clones all
1806 watchers, that means all timers, I/O watchers etc. are active in both
1807 parent and child, which is almost never what you want.
1783 1808
1784SECURITY CONSIDERATIONS 1809SECURITY CONSIDERATIONS
1785 AnyEvent can be forced to load any event model via 1810 AnyEvent can be forced to load any event model via
1786 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used 1811 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1787 to execute arbitrary code or directly gain access, it can easily be used 1812 to execute arbitrary code or directly gain access, it can easily be used

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