[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs.
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC

         time, which might affect timers and time-outs.
         When this is the case, you can call this method, which will update
         the event loop's idea of "current time".
+        A typical example would be a script in a web server (e.g.
+        "mod_perl") - when mod_perl executes the script, then the event loop
+        will have the wrong idea about the "current time" (being potentially
+        far in the past, when the script ran the last time). In that case
+        you should arrange a call to "AnyEvent->now_update" each time the
+        web server process wakes up again (e.g. at the start of your script,
+        or in a handler).
         Note that updating the time *might* cause some events to be handled.
   SIGNAL WATCHERS
        $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
     correctly.
     Example: exit on SIGINT
        my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
+   Restart Behaviour
+    While restart behaviour is up to the event loop implementation, most
+    will not restart syscalls (that includes Async::Interrupt and AnyEvent's
+    pure perl implementation).
+   Safe/Unsafe Signals
+    Perl signals can be either "safe" (synchronous to opcode handling) or
+    "unsafe" (asynchronous) - the former might get delayed indefinitely, the
+    latter might corrupt your memory.
+    AnyEvent signal handlers are, in addition, synchronous to the event
+    loop, i.e. they will not interrupt your running perl program but will
+    only be called as part of the normal event handling (just like timer,
+    I/O etc. callbacks, too).
    Signal Races, Delays and Workarounds
     Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
     callbacks to signals in a generic way, which is a pity, as you cannot do
     race-free signal handling in perl, requiring C libraries for this.
     it's built-in modules) are required to use it.
     That does not mean that AnyEvent won't take advantage of some additional
     modules if they are installed.
-    This section epxlains which additional modules will be used, and how
+    This section explains which additional modules will be used, and how
-    they affect AnyEvent's operetion.
+    they affect AnyEvent's operation.
     Async::Interrupt
         This slightly arcane module is used to implement fast signal
         handling: To my knowledge, there is no way to do completely
         race-free and quick signal handling in pure perl. To ensure that
         10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
         If this module is available, then it will be used to implement
         signal catching, which means that signals will not be delayed, and
         the event loop will not be interrupted regularly, which is more
-        efficient (And good for battery life on laptops).
+        efficient (and good for battery life on laptops).
         This affects not just the pure-perl event loop, but also other event
         loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
         Some event loops (POE, Event, Event::Lib) offer signal watchers
 FORK
     Most event libraries are not fork-safe. The ones who are usually are
     because they rely on inefficient but fork-safe "select" or "poll" calls.
     Only EV is fully fork-aware.
+    This means that, in general, you cannot fork and do event processing in
+    the child if a watcher was created before the fork (which in turn
+    initialises the event library).
     If you have to fork, you must either do so *before* creating your first
     watcher OR you must not use AnyEvent at all in the child OR you must do
     something completely out of the scope of AnyEvent.
+    The problem of doing event processing in the parent *and* the child is
+    much more complicated: even for backends that *are* fork-aware or
+    fork-safe, their behaviour is not usually what you want: fork clones all
+    watchers, that means all timers, I/O watchers etc. are active in both
+    parent and child, which is almost never what you want.
 SECURITY CONSIDERATIONS
     AnyEvent can be forced to load any event model via
     $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
     to execute arbitrary code or directly gain access, it can easily be used

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Comparing AnyEvent/README (file contents): Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs. Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC

Diff Legend

Comparing AnyEvent/README (file contents):
Revision 1.55 by root, Mon Sep 14 05:05:09 2009 UTC vs.
Revision 1.57 by root, Sat Dec 5 02:52:03 2009 UTC