Re: Thread usage cases

>>>>> "BCW" == Bryan C Warnock <[email protected]> writes:

>> 3. Subroutines
>> 
>> sub foo { print "foo" }
>> 
>> Thread1		Thread2
>> foo();		eval 'sub foo { print "bar" }';
>> 
>> This prints either "foo" or "bar". 
>> 
>> Thread2 replaces the coderef for &main::foo. This could happen *while*
>> Thread1 is executing foo(). We can handle this by having Thread1 hold
>> a reference count on the coderef while it is executing foo().

BCW> Hadn't considered this.  Hmmm....

I'd claim, don't do that. And most likely that nothing bad will
happen. Thread1 while in middle of executing the code will not 
even notice that the coderef that is _pointed_ at by ::foo has
been replaced.

The eval is building an optree and storing a pointer in the global
namespace (or package perhaps.)

BCW> (Assuming all program globals, of course.)

BCW> Thread 1: $a = $b + $c;    
BCW> Thread 2: $d = $c / $a;

BCW> Thread 1, doing statement locking, could lock these $a, $b, $c, while
BCW> Thread 2 locks them $d, $c, $a.  Potential deadlock between $a and $c.

This really belongs on -internals.

The visible language issues belongs here.

<chaim>
-- 
Chaim Frenkel					     Nonlinear Knowledge, Inc.
[email protected]				               +1-718-236-0183