From: Eric Jacoboni <jaco@...>
Date: 2008-02-20T22:09:59+09:00
Subject: Ruby 1.9, threads and FreeBSD 5

Hi,

Considering the following theory code:

require "thread"

ping   = ConditionVariable.new
pong   = ConditionVariable.new
mutex  = Mutex.new

1.upto(10) do   # 10 threads pong
  Thread.new do
     mutex.synchronize do
       ping.wait(mutex)
       puts("Pong...")
       pong.signal
     end
   end
end

1.upto(10) do   # 10 threads ping
  Thread.new do
     mutex.synchronize do
       pong.wait(mutex)
       puts("Ping...")
       ping.signal
     end
   end
end

pong.signal   # Go!

Thread.list.each { |t| t.join if t != Thread.main }


This code works as expected with Ruby 1.8 on FreeBSD and OS X : 

% /usr/bin/ruby ping_pong_cond.rb
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...
Ping...Pong...


But it blocks with Ruby 1.9 on both OS :

% ruby ping_pong_cond.rb         
^Cping_pong_cond.rb:30:in `join': Interrupt
	from ping_pong_cond.rb:30:in `block in <main>'
	from ping_pong_cond.rb:30:in `each'
	from ping_pong_cond.rb:30:in `<main>'

Furthermore, it works fine with Ruby 1.9 on Vista.

As i know there is some change in Ruby threads/Native threads between
1.8 and 1.9, i suspect this change could be the culprit...

Any clue?

Thanks