From: Bertram Scharpf <lists@...>
Date: 2007-10-04T19:08:38+09:00
Subject: Re: Signal handling strangeness (Linux)

Hi,

Am Donnerstag, 04. Okt 2007, 18:47:25 +0900 schrieb Han Holl:
> #!/usr/bin/ruby -w
> trap('TERM') do
>   exit
> end
> 
> IO.popen("tail -F --lines=0 --pid=#{Process.pid} /var/log/messages") do |h|
>   while line = h.gets
>     puts line
>   end
> end
> # end-of-program
> 
> cannot [...] be terminated with 'kill -TERM pid'.
> It hangs on a waitpid (or wait4) for the tail process.
> Why is this ? And is it reasonable ?

The wait is part of popen. So, `tail' runs until
Process.pid(==$$) terminates and $$ waits for the `tail' to
finish. It's a deadlock but it's the correct behaviour. You
should state a clear definition which task is to be stopped.
You can offer a pid or a kill command by another feature of
your Ruby application.

I did a lot process and thread scheduling and at least to me
it comes hard every time anew.

Bertram


-- 
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de