From: Luiz Angelo Daros de Luca <luizluca@...>
Date: 2011-06-28T02:28:07+09:00
Subject: Re: Understanding Threading...

Hello Darry,

Is your block using some C extension? In ruby<1.9, threads in ruby do
not use system threads. So, if you call
some external C command, no thread will run in ruby. In ruby>=1.9, it
uses pthreads. Even though, threads in
ruby does not run in parallel. There is a global mutex that makes
every thread runs isolated. Just like a single processor
machine.

In the past, while programming with Qt in Ruby, I did a simple hack in
order to get ruby some processor time when main thread goes loop.

    block=Proc.new{ Thread.pass }
    timer=Qt::Timer.new(window)
    invoke=Qt::BlockInvocation.new(timer, block, "invoke()")
    Qt::Object.connect(timer, SIGNAL("timeout()"), invoke, SLOT("invoke()"))
    timer.start(10)

Regards,

---
     Luiz Angelo Daros de Luca, Me.
            luizluca@gmail.com



2011/6/27 Darryl L. Pierce <mcpierce@gmail.com>:
> I'm working on a use case where I need to spawn a thread that handles a
> blocking piece of communication and have it call back into a lamba
> function when the call completes. All without blocking the main
> application thread.
>
> The code I have is:
>
> class Foo
>
>  def sync(args = {}, &callback)
>    block = args[:block] || false
>    if block
>      Thread.new do
>        # passing in true says to block until the underlying code ends
>        @underlying_impl.sync true
>        callback.call
>      end
>    else
>      @underlying_impl.sync false
>      callback.call
>    end
>  end
>
> end
>
> What I _want_ to have happen is that, if I call this with :block =>
> true, the blocking call would get spawned off on a separate thread and
> run in parallel to the main thread. And, of course, if called with
> :block => false (or without :block at all) that the calling thread would
> block until the sync exits.
>
> However, what I'm seeing is that, even with :block => true, the new
> thread is created but the main thread is blocking. If I put a
> Thread.pass call in just before calling @underlying_impl.sync then the
> main thread updates but the other thread never executes.
>
> Am I misunderstanding Threading in Ruby? In Java spawning a Thread has
> that other thread run in parallel without interaction. Does Ruby not
> work the same way?
>
> --
> Darryl L. Pierce <mcpierce@gmail.com>
> http://mcpierce.multiply.com/
> "What do you care what people think, Mr. Feynman?"
>