On Fri, Feb 13, 2009 at 02:42, Kelvin Philip <kelvinphi...@gmail.com> wrote: > Hi, > > I am calling two seperate fuctions defined under two different perl modules > via two independent threads. Now, I use the $thr->join; command to wait for > the first thread to complete and then start the second. But it seems that > the two module functions are being executed simultaneously. The interpreter > throws error saying that some variables which are used in the second > function is uninitialised. Actually , those were defined in the first > function. My code looks something like this: > > *use threads;* > *use strict;* > *use warnings;* > *use module1;* > *use module2;* > ** > *my $thr1 = threads->new(\&func_module1);* > *$thr1->join;* > ** > *my $thr2 = threads->new(\&func_module2);* > *$thr2->join;* > > Note: The func_module1 & func_module2 are subfunctions defined under moule1 > & module2 respectively. > > Please suggest a solution for this issue. > > Regards, > Kelvin >
Why are you using threads if you desire the code to run sequentially? The only value threads add to a program is the ability to run functions asynchronously. And they add that functionality by increasing the complexity drastically. Also, why is a function in one module setting variables that are to be accessed by another module? This is a bad practice. If the second function needs state information from the first function then the first function should return that information and you should then pass that information to second function. One reason (and it is not even the most important of the reasons) is the one you have run into: threads don't share variables by default. from http://perldoc.perl.org/threads.html The threads API is loosely based on the old Thread.pm API. It is very important to note that variables are not shared between threads, all variables are per default thread local. To use shared variables one must use threads::shared. If you use threads::shared, you must ensure that two threads are not trying to use the same variable at the same time (i.e. you must call lock() on the variable before reading or changing it). Locks are tricky things and it is easy to get into a deadlock situation. A simple case of deadlock occurs when thread 1 wants $foo and has $bar locked and thread 2 has $bar locked and wants $foo. They both will wait forever to get their locks. -- Chas. Owens wonkden.net The most important skill a programmer can have is the ability to read. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
