From: ara.t.howard@...
Date: 2006-07-10T00:15:04+09:00
Subject: Re: Deadlockproblem

On Sun, 9 Jul 2006, Asterix Gallier wrote:

> Hello,
>
> i'm trying to realize asynchronous communication, but the sender have to
> wait until the answer is recieved.

but that's synchronous!  ;-)

seriously, if the send always waits for the answer what good does it do thread
your program?

> My questions:
> - why did this deadlock occur, and how can it be fixed

among other things, you never do anything with @waitQueue - you simply always
set @waitLock to true.

> - is there another/better way for reaching this goal

   harp:~ > cat a.rb
   require 'thread'
   class Oracle
     def initialize
       @questions = Queue.new
       @thread = Thread.new(@questions){|q|
         loop{
           question, answer_with = q.pop
           answer_with[question.to_s + ' 42']
         }
       }
     end
     def ask question, &answer_with
       if answer_with
         @questions.push [question, answer_with]
       else
         q = Queue.new
         ask(question){|answer| q.push answer}
         Thread.new{ q.pop }
       end
     end
     def self.instance(*a, &b) @instance ||= new(*a, &b) end
     def self.ask(*a, &b) instance.ask *a, &b end
   end

   #
   # you can block up front
   #
     n = -1
     p Oracle.ask("something #{ n += 1 }:").value

   #
   # or ask and reap later
   #
     threads = []
     7.times{ threads << Oracle.ask("something #{ n += 1 }:") }
     threads.map{|t| p t.value}


   harp:~ > ruby a.rb
   "something 0: 42"
   "something 1: 42"
   "something 2: 42"
   "something 3: 42"
   "something 4: 42"
   "something 5: 42"
   "something 6: 42"
   "something 7: 42"


regards.

-a
-- 
suffering increases your inner strength.  also, the wishing for suffering
makes the suffering disappear.
- h.h. the 14th dali lama