From: Peter Hickman <peterhi@...>
Date: 2001-08-09T05:58:07+09:00
Subject: [ruby-talk:19393] Re: Trying to get to grips with Ruby threads

Thank you very much. Your code example does just what I was expecting mine
to do.
Thank you again for taking the time to craft such a useful code. Now I will
get on with the rest of the nightmare that I have in mind.

Thanks.

"YANAGAWA Kazuhisa" <kjana@os.xaxon.ne.jp> wrote in message
news:AT8c7.5520$qm1.48139@e420r-atl3.usenetserver.com...
> In message <997216964.15259.0.nnrp-10.9e980a61@news.demon.co.uk>
> peterhi@shake.demon.co.uk writes:
>
> > > Sleeping does not release the mutex... so thread #1 is always going to
> > > be waiting for thread #0 to stop sleeping, as thread #0 owns the
mutex.
> >
> > I thought that as well. However the cv.signal is before the sleep and so
the
> > mutex should be available. Or so I think.
>
> ConditionVariable#signal only signals some condition is met --- Mutex
> is not released.
>
> On ConditionVariable#wait, the caller thread releases Mutex and passes
> execution to another thread which may awake the waiting thread by
> calling ConditionVariable#signal.
>
>
> Indeed, truely critical region in your code is only getting an
> existent job from the bag of jobs.  In this case you don't have to use
> ConditionVariables, like following:
>
>
>     require "thread"
>
>     mutex = Mutex.new
>     work = (1..100).collect { |i| "job #{i}" }
>
>     threads = []
>     2.times do
>       |i|
>       threads << Thread.new(i) do
>         |id|
>         job = nil
>         while true
>           mutex.synchronize do
>             if not work.empty?
>               job = work.pop
>             else
>               job = :nojobs
>             end
>           end
>           break if job == :nojobs
>
>           puts "Thread #{id} gets #{job}"
>           if id == 0
>             sleep(5)
>           end
>         end
>       end
>     end
>
>     threads.each { |t| t.join }
>
>
> But more likely to use Queue which implements a synchronized queue.
>
>
> --
> kjana@os.xaxon.ne.jp                                 August 8, 2001
> Haste makes waste.
>
>