is_joinable question

anaconda_wly has asked for the wisdom of the Perl Monks concerning the following question:

Why main didn't wait until testfun finished in my example below? It seems is_joinable returned false. I found "a call to is_joinable returns true only if a thread has finished running, hasn't been detached and hasn't been joined already". How to judge a running but not join thread?

Hi, Anonymous Monk, I changed my code as below. If I have requirement to judge before join...how to write the condition...

 #/usr/bin/perl -w
use strict;
use warnings;
use threads;
my @arrayRunningThreads = ();
&main;

sub main
{
    my $thrHandle = threads->create(\&detachedThreads);
        $thrHandle->detach();
    push @arrayRunningThreads, $thrHandle;
    for(1...3){
        $thrHandle = threads->create(\&MustJoin);
        push @arrayRunningThreads, $thrHandle;
    }
    
    foreach (@arrayRunningThreads){
        $_->join() if( $_->is_joinable() );
    }

    print "End. \n";
}    
sub detachedThreads
{
    sleep 3;
    print "exiting thread.\n";
}
sub MustJoin
{
    sleep 3;
    print "exiting thread.\n";
}
[download]

 output:
End.
Perl exited with active threads:
        3 running and unjoined
        0 finished and unjoined
        1 running and detached
[download]

Comment on is_joinable question Select or Download Code

Replies are listed 'Best First'.
Re: is_joinable question by Anonymous Monk on Jun 04, 2013 at 04:02 UTC
main did not wait because is_joinable returned false, so you didn't join if you want to wait for $thrHandle, simply join, join blocks, join waits until the thread over, until it is_joinable Study this example Re^2: Thread parallel execution (joinable)	[reply]
Re^2: is_joinable question by anaconda_wly (Scribe) on Jun 04, 2013 at 06:03 UTC
example you give works, but I didn't understand difference between threads->list( threads::joinable ) and is_joinable yet `while( threads->list ) { for my $joinable ( threads->list( threads::joinable ) ) { $joinable->join; } }` [download]	[reply] [d/l]
Re^3: is_joinable question by MidLifeXis (Monsignor) on Jun 04, 2013 at 13:06 UTC
I can ask my kids "is mom home yet?" and get a yes or no answer. I can also ask them to wait outside until their mom gets back. The first is like `is_joinable`, the second is like `join`. One gets a yes or no answer, the other blocks until it is done. Update: Ignore me. Didn't read the question completely. --MidLifeXis	[reply] [d/l] [select]
Re^3: is_joinable question by Anonymous Monk on Jun 05, 2013 at 06:03 UTC
example you give works, but I didn't understand difference between threads->list( threads::joinable ) and is_joinable yet Ok, and then what happened? Do you have a question? What do you understand? Do you understand the difference between a while loop and an if statement?	[reply]
Re: is_joinable question by Anonymous Monk on Jun 05, 2013 at 06:50 UTC
The correct way to write that loop `while( @arrayRunningThreads ){ my @keepers; for my $thread ( @arrayRunningThreads ){ if( $thread->is_joinable() ){ $thread ->join; } elsif( not $thread ->is_detached ){ push @keepers, $thread; } } @arrayRunningThreads = @keepers; }` [download] If you don't add detached threads you can write it as `while( @arrayRunningThreads ){ my @keepers; for my $thread ( @arrayRunningThreads ){ if( $thread->is_joinable() ){ $thread ->join; } else { push @keepers, $thread; } } @arrayRunningThreads = @keepers; }` [download] Or the functional equivalent of what the above code does, relying on the fact that join blocks until a thread is_joinable `for my $thread ( @arrayRunningThreads ){ $thread->join; }` [download]	[reply] [d/l] [select]