From: "Ara.T.Howard" <ahoward@...>
Date: 2004-02-26T02:04:53+09:00
Subject: Re: io/nonblock - blocks w/threads?

On Wed, 25 Feb 2004, Robert Klemme wrote:

> 
> Some answers - but not all...

thanks for the response...

> That's an interesting question.  One would rather expect
> "Thread.critical=true" to block the whole process.  I guess, that there are
> no thread context changes without these methods and assigning to
> Thread.critical has the side effect of doing a context switch if possible.
> I'd try to use "Thread.pass" after "l.configure..." instead of
> "Thread.critical" to give other threads a chance to run and see what
> happens.
> 
> >   b) is this approach (critical section) the correct way of dealing with
> this
> >   issue?
> 
> If the blocking is indeed caused by the loop spinning endlessly, Thread.pass
> is a far better alternative.  You could as well use sleep to achieve the
> same.

it's the actual call to nonblock that blocks the process, try this using the
two different approaches between the print statements:

  require 'tk'
  require 'open3'
  require 'io/nonblock'
  require 'thread'
  $VERBOSE=nil
  STDOUT.sync = STDERR.sync = true

  r=TkRoot.new
  l=TkLabel.new r, :text=>`ruby -e "p Time.now"`
  l.pack

  command='ruby -e "loop{p Time.now; sleep 1}"'
  i,o,e = Open3::popen3 command
  i.close
  text = nil

  Thread.new do
    loop do 
      rios, = select [o, e], nil, nil
      rios.map do |rio|
        next if rio.eof?
  p 'start...'
        rio.nonblock{ text = rio.read }               # blocks
        #text = rio.gets                                 # does not block
  p 'finish'
        l.configure :text=>text
      end
    end
  end

  Tk.mainloop


i also tried a couple of ways on inserting Thread.pass - outside of nonblock's
block, inside of it, etc. - nothing works except protecting the call to read
by critical/exclusive which does really make sense since the point of nonblock
is not to?


-a
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