From: MenTaLguY <mental@...>
Date: 2008-03-25T01:07:37+09:00
Subject: Re: Thread#raise, Thread#kill, and timeout.rb are unsafe

On Mon, 24 Mar 2008 22:17:34 +0900, Daniel DeLorme <dan-ml@dan42.com> wrote:
> I think the specific problem mentionned was that asynchronous exceptions
> can abort the cleanup within an ensure section. So what about a simple
> solution to that specific problem, like: if an asynchronous exception is
> raised inside an ensure section, the exception is queued and raised at
> the end of the ensure section. Is that too naive?

Maybe slightly.  I don't think it would necessarily be an issue for the
current implementation of 1.9, but you do also need to do the
registration/unregistration of ensure and catch clauses in an
uninterruptible fashion.

Basically you need to have the equivalent of this:

 Thread.uninterruptable do
   begin
     Thread.interruptable do
       # ...
     end
   rescue
     # ...
   ensure
     # ...
   end
 end

(in cases where the thread is currently interruptable)

See also section 4.2 of "Asynchronous Exceptions in Haskell":

 http://citeseer.ist.psu.edu/415348.html

-mental