From: ara.t.howard@...
Date: 2007-01-04T13:12:38+09:00
Subject: Re: Problem in Unit Testing Methods that start new threads

On Thu, 4 Jan 2007, Hemant Kumar wrote:

>
> Since We are calling new each time, even using instance variables won't
> solve the race condition. I have even tried using class variables, and I am
> still getting race condition.
>
> Ara, please demonstrate how you would solve the race condition in above
> shown code of yours?
>

hi hemant-

without thinking too hard about it i'd probably do something like this:


   harp:~ > cat a.rb
   require 'sync'
   require 'thread'

   class Module
     def tattr a
       module_eval <<-code
         def #{ a }= arg
           synchronize(:EX){ @#{ a } = arg }
         end
         def #{ a }
           synchronize(:SH){ @#{ a } }
         end
       code
     end
   end

   class C
     include Sync_m

     tattr :thread

     def initialize
       @thread = nil
       sync_initialize
     end

     def new_thread
       q = Queue.new
       Thread.new{ q.push( self.thread = Thread.current ) }
     ensure
       q.pop
     end
   end

   4242.times{|i| raise "race @ loop #{ i } condition!" unless((c = C.new) and (Thread === c.new_thread) and c.thread) }

   p 42

   harp:~ > ruby a.rb
   42

   harp:~ > ruby a.rb
   42

   harp:~ > ruby a.rb
   42

   harp:~ > ruby a.rb
   42


the methodology of waiting for the 'q.push' is useful so your method only
returns after the thread has 'started' running.

kind regards.

-a
-- 
if you find yourself slandering anybody, first imagine that your mouth is
filled with excrement.  it will break you of the habit quickly enough. - the
dalai lama