From: Robert Klemme <shortcutter@...>
Date: 2010-02-16T00:47:27+09:00
Subject: Re: Mutex

2010/2/15 Mido Peace <mido.peace@gmail.com>:
> require 'thread'
> class Semaphore
>
>  Thread.abort_on_exception = true

Why do you place that inside the class?  This is a global setting.

>  attr_accessor :permits, :mutex, :cv
>
>  def initialize ( permits )
>
>      @permits = permits
>      @mutex = Mutex.new
>      @cv = ConditionVariable.new
>
>  end
>
>
>  def acquire()
>
>    raise "Interrupted Thread " if (!Thread.current.alive?)
>    @mutex.synchronize {
>    while @permits < 1
>       @cv.wait(@mutex)
>    end
>    @permits = @permits - 1
>    }
>  end
>
>  def release()
>    @mutex.synchronize{
>
>      @permits += 1
>      @cv.signal
>
>      }
>
>  end
>
> end
>
> ...
> class Process < Thread
> ...
> def initialize()
>  super(){
>     ...
>     @sem=Semaphore.new(0)

IIRC semaphores are typically initialized with a positive value, i.e.
something larger than 0.  If you think about it, init with 0 does not
make too much sense.

>     ...
> }
> end
>
> def run()
>
> ...
> @sem.acquire()
>
> end
>
>
> The problem is that I should call the semaphore later , not within
> initialization of the process !!

You can't define a class Process like this because that class exists already.

One more hint: for more robust access I suggest to add this method to
your Semaphore class:

def synchronize
  acquire

  begin
    yield
  ensure
    release
  end
end


Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/