From: Robert Klemme <shortcutter@...>
Date: 2012-05-16T16:27:39+09:00
Subject: Re: How to ensure that a block runs entirely after other threads? (Thread.exclusive does not "work")

On Tue, May 15, 2012 at 5:36 PM, Iņaki Baz Castillo <ibc@aliax.net> wrote:
> Hi, I expected that in the following example code, thread t1 would not
> work until the Thread.exclusive blocks ends, but I am wrong:
>
> --------------------------------------
> t1 = Thread.new { loop do printf "." ; sleep 0.1 end }
>
> Thread.exclusive do
>  puts "entering Thread.exclusive..."
>  sleep 2
>  puts "exiting Thread.exclusive"
> end
>
> t1.join
> --------------------------------------
>
>
> But thread t1 runs every 0.1 seconds so I've don't properly understood
> the doc about Thread.exclusive. So, is there any easy way for telling
> Ruby "run this block entirely without passing the GVL to other thread
> in the middle of the block"?

Do I understand that correctly that you want to have 1 thread run
exclusively in the interpreter?  If that's the case I agree with Eric:
that's a bad idea.  You only need to synchronize access to shared
resources.  If there are threads which do not access the shared
resource there is no point in blocking them.

I do not know your sharing and exclusiveness requirements but one
helpful option might be a read write lock.  Or, of course, a regular
mutex.  In any case you need to define in code which threads share
which resources and hence require exclusive access.

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/