From: MenTaLguY <mental@...>
Date: 2007-05-12T06:53:59+09:00
Subject: Re: basic threading question: can ruby use real threads?

On Sat, 12 May 2007 03:46:58 +0900, Joel VanderWerf <vjoel@path.berkeley.edu> wrote:
> This is disturbing.
> 
> Is #timeout inherently unsafe, if it is implemented as a thread, even in
> MRI ruby's green threads?

Correct.  #timeout as presently implemented is NEVER safe to use.
 
> What if there were two kind of ensure clauses, one which is
> uninterruptible (to be used only for cleanup that is deterministic) and
> one which is interruptible (and not guaranteed to finish)?

Nope, that's still not sufficient.  The fundamental problem is that other threads can _arbitrarily_ mess with control flow by injecting exceptions via Thread#raise.  There's no way to guarantee invariants will be preserved, no matter how clever your ensure implementation is.

-mental