Monks,

I have a daemon that runs on a machine, with several sockets open to other nodes. We have a problem that when the system goes down (via reboot, shutdown, or the like), the socket gets hung up on the other side - I have been told this is a known problem with tcp sockets...

Anyway, the program basically runs in a infinite loop, looping on an IO::Poll call waiting for events on the sockets. I have installed sig handlers for INT, KILL, and TERM. The sig_handler basically sets a global variable that indicates the signal that was caught, and on every loop I check the global, and exit the loop if I got a signal. This seems to work when I send a signal via kill -TERM.

What doesn't work is when I reboot or shutdown the machine - my program doesn't seem to get the signal - the man page for shutdown and reboot seem to indicate that all processes are sent the TERM signal to allow them to shut down, etc., but I don't seem to be able to trap it.

Oh yeah, I'm running Linux (kernel rev 2.4.19)

(Apologies that it's a bit more OS'y than Perl'y)

The folllowing code illustrates what I'm doing:

#!/usr/bin/perl
my $sig;

print "my pid: $$\n";

$SIG{TERM} = \&handler;

while(1)
{
    if ($sig)
    {
         last;
    }

    select(undef, undef, undef, .2); # sleep for .2 sec
}

# clean up here
`echo $sig > /tmp/sig.out`; # to check after reboot if it caught it
exit;

sub handler
{
    $sig = shift;
}

[download]

Any thoughts?

--
3dan

In reply to (slightly OT) catching SIGTERM when system goes down by edan

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