From: Caleb Clausen <vikkous@...>
Date: 2008-09-22T07:18:27+09:00
Subject: Re: ThreadError: not owner

Hmmm. I'm guessing that the ability to use a Mutex like a semaphore
wad taken away when the Mutex class was rewritten in c. A Semaphore
class should have then also been added to cover this other use case,
if that ability has to be removed, but I don't see one in my
installation. Signalling is the other important use case for
semaphores besides mutual exclusion. I'd say this is a bug. (But then,
who am I?)

Luckily for you, there's an implementation of Semaphore in ruby here:
http://www.imasy.or.jp/~fukumoto/ruby/semaphore.rb

I can't vouch for that code at all. Note that since it's written in
ruby, it's going to be very slow, compared to the new mutexes... but
then you were using the old (slow) mutexes before so at least you
should be no worse off. Also, Thread.critical is very bad for jruby,
so don't use this there.

You'll have to create a separate variable to hold the semaphore,
something like this: (untested!)

m=Mutex::new
sem=Semaphore.new
Thread.new {
 # something1
 sem.signal
 # something2
}
sem.wait
m.synchronize{}

Maybe you don't even need the mutex at all now. I can't tell from this
little example.