From: Adam Bender <abender@...>
Date: 2008-03-26T02:04:43+09:00
Subject: Re: thread.rb

On Tue, Mar 25, 2008 at 7:57 AM, Robert Klemme
<shortcutter@googlemail.com> wrote:
> 2008/3/25, Adam Bender <abender@gmail.com>:
>
> > I want to modify the Queue class in thread.rb, so I first searched for
>
>  Why?
>
What what?  I want to modify the class as described below; I searched
for the file so I could see how pop was implemented and the class
variables it used.


>  >  P.S. On a related note, I want to add a method to the Queue class that
>  >  is similar to pop, but will take a timeout value and return nil if it
>  >  no item is push'ed before timeout seconds have elapsed.    Can anyone
>  >  suggest something better than the following:
>  >
>  >  class Queue
>  >   def pop_with_timeout(timeout)
>  >     elapsed = 0.0
>  >     while (Thread.critical = true; @que.empty?)
>  >       @waiting.push Thread.current
>  >       Thread.critical = false
>  >       elapsed += sleep(timeout - elapsed)
>  >       puts elapsed
>  >       return nil if elapsed >= timeout
>  >     end
>  >     @que.shift
>  >   ensure
>  >     Thread.critical = false
>  >   end
>  >  end
>  >
>  >  That was the first thing I came up with, and I'm (again) surprised
>  >  that it works - why does sleep ever return less than 1?  What
>  >  interrupts it?
>
>  I opt against using Thread.critical because this is a global exclusive
>  lock on all threads and it is unlikely to continue to exist in the
>  light of JRuby and others. I'd rather use Mutex#try_lock or Monitor's
>  #wait with timeout parameter.

The Queue class uses Thread.critical.  Though I guess writing a queue
using a Monitor would be easy enough to do.

Adam