Hello monks! Long time fan, first time poster.

I've got a code snipped that shows that threads::join() appears to be non-interruptible, which seems to be at odds with the alarm perldoc. When this code runs, it just hangs, as the SIGALRM is never delivered. If I replace the call to join() with a while(1){}, then the alarm is delivered properly. I'm running perl 5.16.3.

I posted this over at StackOverflow, here, before I thought to post it to the Monks. Someone gave me an answer which seems perfectly plausible, but isn't very satisfactory given that other system calls are interruptible, and pthread_join is interruptible. Despite the answer I got on SO, I'm questioning its accuracy because I've found plenty of examples on the web of other people claiming that this is a perfectly reasonable thing to do, and I'm assuming at least one of them actually tried running their code before memorializing it on the Internet.

#!/usr/bin/env perl

use strict;
use warnings;
use threads;

sub worker
{
    print "Worker thread started.\n";
    while(1){}
}

my $thread = threads->create(\&worker);

print "Setting alarm.\n";
$SIG{ALRM} = sub { print "Alarm!\n" };
alarm 2;

print "Joining.\n";
$thread->join();

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In reply to Why does threads::join block SIGALRM by CDahn

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