From: Daniel Fort <naquad@...>
Date: 2009-07-10T13:17:32+09:00
Subject: Re: tcp server with multithreading

> Creating a new socketpair/pipe is pretty too much imho (no matter it's a 
> very
> small object, but it exists and must be handled). I thought about some 
> kind of
> semaphore, then process would look like:
> 
> in thread:
> 
> semaphore.wait_for_event
> 
> in main:
> 
> semaphore.emit_event
> 

I've found the way how to do this, here is code + example:

#!/usr/bin/ruby -w

require 'thread'

class MassSemaphoreEmulator
  def initialize
    @mutex=Mutex.new # we can have race condition on a variable below, 
so avoid it with mutex
    @waiting_threads=[]
  end

  def wait
    @mutex.synchronize { @waiting_threads<<Thread.current } # add 
current thread to waiting ones
    Thread.stop
  end

  def signal
    @mutex.synchronize do # wakeup all threads
      @waiting_threads.each {|t| t.wakeup}
      @waiting_threads.clear
    end
  end
end

semaphore=MassSemaphoreEmulator.new

threads=(1..10).map do |i|
  Thread.new(i*1) do |v|
    print "#{v} is waiting...\n"
    semaphore.wait # wait for our mutex
    print "#{v} got signal.\n"
  end
end

semaphore.signal # get all waiting threads up

threads.each {|t| t.join}


I've also tried to do something with ConditionalVariable, but no luck,
it didn't stop waiting threads.

now I need to find a way for interrupting select call
-- 
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