From: Hans Fugal <fugalh@...>
Date: 2003-09-24T22:38:58+09:00
Subject: Re: When threads block

On Tue, 23 Sep 2003 18:45:40 -0600, Hans Fugal wrote:

> It's difficult to do any serious multi-threaded network programming when
> the whole process blocks on system calls like read, write, and select. Is
> this on a TODO list somewhere, or should I just accept it as a fact of
> life? (and that may mean using a different language.)

Ok, I jumped the gun just a little. On linux /most/ things don't block.
But /some/ things do. e.g.

thread = Thread.new do
    fifo = File.open("fifo","r")
    l = fifo.readline
    puts "#{Time.new} #{l}"
end

puts "#{Time.new} bar"
thread.join

Will block the entire process until the fifo is open. The following
variation does not block the entire process, though:

fifo = File.open("fifo","r")
thread = Thread.new do
    l = fifo.readline
    puts "#{Time.new} #{l}"
end

puts "#{Time.new} bar"
thread.join

I say "most" because that's what the wise ones on #ruby-lang said, and
indeed were surprised to see I had a counter example.

Is there a list of these sorts of things? I need to know what to expect if
I'm going to be able to use ruby for this (soft) real-time application.