Re: Thread-safe modules and callbacks

Are you talking about a callback function that needs to keep track of some state, as in this example:

our $count = 0;
sub my_callback {
  warn "I've been called ".(++$count)." times\n";
  ...
}
my $thread = threads->create(..., \&my_callback);
$thread->join;

print "count = $count\n"; # prints 0
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And the issue that this won't work in a threaded-environment because the $count that gets updated is only accessible in one thread (since it is not declared as shared.) So, callbacks have to be thread-aware if they are going to be used in a threaded environment.

Interesting problem...

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Re^2: Thread-safe modules and callbacks by Saladino (Beadle) on May 09, 2008 at 23:22 UTC
Exactly that! Don't know if possible, it may be possible to access local variables of a function and that could let us delcare as shared dynamically callbacks variables. but that doesn't solve the problem when callback acess main threads variables.	[reply]
Re^3: Thread-safe modules and callbacks by pc88mxer (Vicar) on May 09, 2008 at 23:30 UTC
How about switching to objects, and create a closure for your callback: `use threads::shared; my $obj = bless {}, 'foo'; sub foo::callback { warn "I've been called ".++($_[0]->{count})." times\n"; } share($obj); # only needed in a threaded environment my $thread = threads->create('start_thread', sub { $obj->callback(@_) +} ); $thread->join; print "count = ", $obj->{count}, "\n"; # prints 3 sub start_thread { my $cb = shift; for (1..3) { $cb->() } }` [download] Is there a way to implement function call behavior for a blessed reference? If so, you could have the best of both worlds.	[reply] [d/l]