From: Tanaka Akira <akr@...>
Date: 2011-06-15T15:29:09+09:00
Subject: [ruby-dev:43820] mysterious hang at busy loop after system()

以下のようなプログラムが手元の環境のひとつでハングします。

不思議なことに、先頭の system('true') を取り除くとハングしません。

% cat y.rb
system('true')

raised = false
t = Thread.new do
  raised = true
  loop { }
end

begin
  raise
rescue
  until raised || !t.alive?
    Thread.pass
  end
end
% ./ruby y.rb
^C^C^C^C^C^Z
zsh: suspended  ./ruby y.rb
% kill -9 %1
%
[1]  + killed     ./ruby y.rb
% ./ruby -v
ruby 1.9.3dev (2011-06-15 trunk 32099) [x86_64-linux]
% uname -mrsv
Linux 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:24 UTC 2011 x86_64
% lsb_release -a
LSB Version:
core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 11.04
Release:        11.04
Codename:       natty
-- 
[田中 哲][たなか あきら][Tanaka Akira]