From: "Jakub Pavlík jn." <severus@...>
Date: 2009-01-19T03:04:10+09:00
Subject: Thread starvation

Hello,

In my game freeVikings [http://freevikings.sf.net] I have code listed below.
It uses threads and sometimes problem known as "thread starvation" occurs.
Does anyone know some solution?
(A more detailed description is under the code listing.)

----------------------------------
def do_loading(&block)
  Thread.abort_on_exception = true

  load_t = Thread.new {
    Thread.current.priority = 1
    Thread.stop

    block.call
  }

  progressbar_t = Thread.new {
    Thread.current.priority = 2
    load_t.run

    loop {
      paint_loading_screen @app_window, true
      sleep 0.3
    }
  }

  load_t.join
  Thread.kill progressbar_t
end
----------------------------------

It's an instance method of class Game and is used in this way:
a_game.do_loading {
  # load something here
}

Purpose of this method is to show a simple progressbar while doing some 
long-lasting operation (e.g. loading new level).

It creates two threads: load_t, in which given block is executed
and progressbar_t, which regularly calls Game#paint_loading_screen 
(method, which repaints loading screen with progressbar).

Thread progressbar_t has higher priority, because I need it to be called
often and not to e.g. wait for load_t's end.

Unfortunatelly from time to time Thread load_t is somehow "suspended" - 
progressbar shows progress on and on, but nothing happens.
I think it's a case of so called "thread starvation" and would be very glad
to know how to avoid it.

Thank you very much.

Jakub Pavlik

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